Contributions to Late Cretaceous Paleontology and Stratigraphy of New Mexico Part II

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Contributions to Late Cretaceous paleontology and stratigraphy of New Mexico Part II

SOCORRO 1988 11

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Contents

The Late Cretaceous ammonite Spathites Kummel & Decker in New Mexico and Trans-Pecos Texas W. A. COBBAN 5-21

The Late Cretaceous ammonite Romaniceras Spath, 1923, in New Mexico W. J. KENNEDY & W. A. COBBAN 23-34

Middle Cenomanian (Late Cretaceous) molluscan fauna from the base of the Boquillas Formation, Cerro de Muleros, Dona Ana County, New Mexico W. J. KENNEDY, W. A. COBBAN & S. C. HOOK 35-44

The Late Cretaceous ammonite Spathites Kummel & Decker in New Mexico and Trans-Pecos Texas

W. A. Cobban

U.S. Geological Survey, Mail Stop 919, Box 25046, Federal Center, Denver, Colorado 80225, U.S.A.

Abstract—Spathites was established for S. chispaensis Kummel & Decker, 1954, which is a synonym of Pseudotissotia? coahuilaensis Jones, 1938. Spathites is known in the United States only from rocks of middle Turonian age in New Mexico and western Texas. At least three chronologic species are present, from oldest to youngest S. rioensis Powell, S. coahuilaensis (Jones), and S. puercoensis (Herrick & Johnson). The first two have subpseudoceratitic sutures, whereas S. puercoensis has a decidedly pseudoceratitic suture. Spathites rioensis occurs in the subzone of Collignoniceras woollgari woollgari (Mantell), and S. coahuilaensis is found in the younger subzone of C. woollgari regulare (Haas). Spathites puercoensis occurs still higher in the zone of Prionocyclus hyatti. Rare inner whorls from two localities in New Mexico suggest the possibility of a fourth species that may lie between the zones of C. woollgari and P. hyatti.

Introduction Pecos Texas. These localities are shown in Fig. 1, and data The genus Spathites was proposed by Kummel & Decker concerning the localities are given in Table 1. Prefix D in- (1954) for medium-sized, stout, involute ammonites that dicates Denver Mesozoic locality numbers; the rest are have inner whorls ornamented by ribs and tubercles (um- Washington, D.C., Mesozoic locality numbers. bilical and inner and outer ventrolateral) and outer whorls with reduced ornament. The suture is simplified. Kummel Sequence of species & Decker based their genus on S. chispaensis, which they The oldest known species of Spathites in North America is described as a new species from Trans-Pecos Texas and Powell, which occurs in the lower part of the Chihuahua, Mexico. S. rioensis Kennedy, Wright & Hancock (1980a) dealt extensively middle Turonian zone of Collignoniceras woollgari (Mantell). with the genus and noted that it had a time span of latest This zone was divided into a lower subzone of C. woollgari Cenomanian to middle Turonian and a geographic range woollgari (Mantell) and an upper one of C. woollgari regulare from North America to Europe, northern Africa, and east (Haas) (Cobban & Hook, 1979). An early form of S. rioensis across southern U.S.S.R. to southern India. Those authors was found at the base of the subzone of C. woollgari woollgari recognized the following species: Spathites (Spathites) chis- in western New Mexico (Fig. 1, locs. 6, 7). Specimens of paensis Kummel & Decker, S. (S.) rioensis Powell, S. (S.) this early form were assigned to Spathites aff. subconciliatus puercoensis (Herrick & Johnson), S. (S.) sulcatus (Wiedmann), (Choffat) (Cobban & Hook, 1983: 6), but in the present report they are better reassigned to S. (Jeanrogericeras) reveliereanus (Courtiller), and S. (J.) sub- S. rioensis. conciliatus (Choffat). Spathites coahuilaensis (Jones) has been found in the sub- Spathites is locally abundant in west-central and western zone of Collignoniceras woollgari regulare in west-central and New Mexico, where three chronologic species are known, western New Mexico. At locality D11450 (Fig. 1, loc. 32), from oldest to youngest S. rioensis, S. coahuilaensis (Jones), S. coahuilaensis was collected 7.3 m above beds that contain and S. puercoensis. The last species is especially common in C. woollgari woollgari. the Semilla Sandstone Member of the Mancos Shale in the Spathites puercoensis (Herrick & Johnson) has been found Rio Puerco valley northwest of Albuquerque. only in the youngest middle Turonian zone of Prionocyclus The present study was undertaken to more fully docu- hyatti (Stanton). Among the ammonites associated with S. ment the presence of Spathites in New Mexico and Trans- puercoensis are the forms illustrated by Kennedy, Wright & Pecos Texas. Collections on which this study was based Hancock (1980b, text fig. 2, pl. 45, figs. 1, 2) as Shuparoceras were made by many geologists of the U.S. Geological Sur- sp. nov. (Fig. 1, loc. 17) and Romaniceras (R.) kallesi (Záz- vey and the New Mexico Bureau of Mines & Mineral Re- vorka) (Fig. 1, loc. 16), both of which are herein reassigned sources. The largest collections were made by W. T. Lee to Romaniceras (R.) mexicanum Jones, 1938. in 1905, T. W. Stanton and J. G. Walthers in 1906, C. B. None of the American species of Spathites is known from Hunt and assistants in 1930-31, C. H. Dane in 1963, and S. Europe, where the genus also seems to be confined to the C. Hook, E. A. Merewether, N.A. La Fon, and me in 1978. middle Turonian. In the type region of the Turonian, Sau- All photographs were made by Robert E. Burkholder of murois and Touraine in northwestern France, two species, the U.S. Geological Survey. Drawings of sutures were S. (Jeanrogericeras) reveliereanum (Courtiller) and S. (J.) com-besi made by me. (Sornay), are present in the Tuffeau de Saumur at the same stratigraphic level as the ammonites Lewesiceras peramplum Geographic distribution (Mantell), Fagesia rudra (Stoliczka), Neoptychites cephalotus (Courtiller), N. xetriformis Pervinquiere, Kamerunoceras Spathites is present in 49 collections of fossils in the U.S. turoniense (d'Orbigny), Romaniceras kallesi Zazvorka (basal Geological Survey's collections from New Mexico and Trans- part of range), Tragodesmoceras courtilleri Amédro & Badillet,

Collignoniceras woollgari (Mantell), C. carolinum (d'Orbigny), 1938. Pseudotissotia(?) kellyi Jones, p. 124, pl. 9, figs. 2, 7, pl. 10, fig. 9 and Lecointriceras costatum Kennedy, Wright & Hancock (not pl. 8, fig. 3). (Amédro & Badillet, 1982, fig. 5). 1954. Spathites chispaensis Kummel & Decker, p. 311, p1. 30, figs. 1, 2, pl. 31, figs. 1-15, text-fig. 1. 1954. Spathites coahuilaensis (Jones): Kummel & Decker, pp. 311, Systematic paleontology 312. The specimens illustrated in this report are stored in the 1954. Spathites kellyi (Jones): Kummel & Decker, pp. 311, 312. 1980a. National Museum of Natural History in Washington, D.C., Spathites chispaensis Kummel & Decker: Kennedy, Wright & where they have USNM catalog numbers. Hancock, p. 822, text-figs. la, b, 8B. In the descriptions and illustrations of sutures, E stands Types-Holotype University of Michigan 16822, from for the external lobe, L stands for the lateral lobe, E/L Coahuila, Mexico (locality and stratigraphic position un- stands for the saddle that separates the external and lateral known). Hypotypes: USNM 404344 from the Chispa Summit lobes, U stands for the umbilical lobe (with U, and U2 as Formation at Sobaco, Chihuahua, Mexico; USNM 404336, divisions), and I stands for the internal lobe. In the drawings 404339, 404341, and 404343 from the Chispa Summit For- of sutures, the heavy straight line marks the middle of the mation in Jeff Davis County, Texas; USNM 404337 and venter, the lighter straight line marks the middle of the 404338 from the Tres Hermanos Formation in Cibola County, dorsum, the dashed line marks the umbilical shoulder, and New Mexico; and USNM 404340 and 404342 from the Rio the evenly curved solid line marks the umbilical seam. Salado Tongue of the Mancos Shale in Cibola and McKinley All dimensions are in millimeters. Figures in parentheses Counties, New Mexico. after the umbilical width represent percentage of the total Description-Spathites coahuilaensis is characterized by its diameter of the shell. adult body chamber that has smooth, flattened flanks; sharply defined ventrolateral shoulder; and broad, flat venter crossed Family ACANTHOCERATIDAE de Grossouvre, 1893 transversely by broad, low folds. [1894] Subfamily MAMMITINAE Hyatt, 1900 The holotype is a well-preserved internal mold of a stout Genus SPATHITES Kummel & Decker, 1954 adult that consists of the phragmocone and about half of ( = Spathitoides Wiedmann, 1960) the body chamber. Jones (1938: 123) gave its diameter as 89 mm and its umbilicus as 9 mm. Whorls are higher than Type species-By original designation, Spathites chispaen- wide with flattened flanks, well-defined ventrolateral sis Kummel & Decker, 1954, from the lower Turonian of shoulder, and broad, flattened venter. Greatest width is a Chihuahua, Mexico; = Pseudotissotia? coahuilaensis Jones, little below the middle of the flank. Ornament is lacking on 1938, from the lower Turonian of Coahuila, Mexico. the outer whorl of the phragmocone and on the body Diagnosis-Medium-sized, involute, stout to com- chamber except for prorsiradiate striae on the body pressed ammonites that have inner whorls with ribs and chamber and broad, low, transverse folds on the venter. tubercles (umbilical and inner and outer ventrolateral) and These folds are narrower than the interspaces and number later whorls with reduced ornament or even loss of orna- about 20 per whorl. Most of the external suture is ment. Venter flat or concave. Suture simple with broad bifid preserved (Fig. 4A). Only bits of the external lobe (E) are E/L and narrow to moderate L that is either poorly bifid or visible, and the drawing by Jones (1938, pl. 9, fig. 1) of that denticulate; sutures of some specimens pseudoceratitic. lobe is restored and too generalized. The lateral lobe (L) Remarks-Kummel & Decker (1954: 312) noted that and the umbilical lobes (U2 and U,) are narrow and little their species, S. chispaensis, the type species of Spathites, could divided. Saddles that separate these lobes as well as the E/L be conspecific with the ammonite from Mexico described as saddle are very broad, bifid, and little divided. Pseudotissotia? coahuilaensis Jones (1938: 123, pl. 9, figs. 1, 3, 8). Remarks-Spathites coahuilaensis is present in small num- A comparison of a plaster cast of Jones' holotype to bers in the Chispa Summit Formation in Trans-Pecos topotypes of S. chispaensis reveals no specific differences, and Texas. The specimens occur in septarian limestone Kummel & Decker's species is herein considered a junior concretions and in unusual hiatus concretions (Kennedy et synonym of S. coahuilaensis. al., 1977). Specimens in the septarian concretions usually Kennedy, Wright & Hancock (1980a) recognized two have fairly good early whorls, but the later septate whorls subgenera of Spathites, Spathites (S.) with S. chispaensis as the and body chambers are broken and distorted. Specimens in type and S. (Jeanrogericeras) with Ammonites reveliereanus the hiatus concretions are mostly undistorted body Courtiller, 1860, as the type. Spathites (S.) includes forms chambers. Most specimens closely resemble the holotype as that have smooth adult body chambers with sharp ventral well as the specimens illustrated by Kummel & Decker shoulders, and S. (J.) includes forms that retain ribs and (1954) as S. chispaensis. A fragment of a body chamber from tubercles on the outer whorls. Spathites (Jeanrogericeras) one of the hiatus concretions is larger than any described (Wiedmann, 1959: 740) is the older form and presumably specimen and has a venter 33 mm wide (Fig. 2I-K). gave rise to S. (Spathites) (Kennedy et al., 1980a: 833-835, Inasmuch as this fragment indicates an adult about twice as fig. 9). Spathites puercoensis, the youngest of the American large as the smallest adult (Fig. 2A, B) from the hiatus species, retains ornament on the adult whorls and in this concretions, sexual dimorphism is suggested. respect resembles Jeanrogericeras. However, S. puercoensis is Spathites coahuilaensis occurs sparingly in the Mancos Shale younger than S. chispaensis [coahuilaensis], the type of Spath- in west-central and western New Mexico (Fig. 1, locs. 2, 3, ites (S.), and has a broader venter, narrower umbilicus, and 6, 33). Two specimens, that have diameters of 48 and 91 more pseudoceratitic suture than Jeanrogericeras. Until more mm, are especially noteworthy in that they further suggest is known about the relationship of Jeanrogericeras to Spath- dimorphism. The smaller one (Fig. 3R, S) has nearly three- ites, no attempt is made in the present study to assign the fourths of a whorl of body chamber that has a diameter of American species to subgenera of Spathites. about 32 mm at its base. Ribs disappear and umbilical tubercles weaken greatly at the beginning of the body cham- SPATHITES COAHUILAENSIS (Jones) ber. Ventrolateral tubercles, although weakened, are still Figs. 2A-N, 3P-Y, 4 present on the youngest preserved part of the body cham- 1931. Pseudotissotia(?) n.sp. Adkins, p. 58, pl. 2, fig. 5, pl. 4, figs. 3, ber, which also has low transverse ventral ribs. The larger 6. specimen (Fig. 2L-N) consists of a phragmocone and a little 1938. Pseudotissotia(?) coahuilaensis Jones, p. 123, pl. 9, figs. 1, 3, less than one-half whorl of body chamber, which has a diameter of 66 mm at its base. This specimen (macroconch)

11 is twice as large as the smaller one (microconch). All ornament, except for broad transverse ventral folds, has disappeared before the beginning of the last complete whorl on the larger specimen. Sutures of S. coahuilaensis from Trans-Pecos Texas (Fig. 4D) and New Mexico (Fig. 4C) resemble that of the holotype (Fig. 4A) and that of a topotype (Fig. 4B) of S. chispaensis Kummel & Decker [coahuilaensis] in their general form and simplicity. The lateral lobe (L) is fairly narrow, poorly bifid, and little divided. Umbilical lobes (U, and U2) are small and quite simple. The E/L saddle is broad and bifid, and other saddles are bifid and tend to be broad. Occurrence-Spathites coahuilaensis occurs in Trans- Pecos Texas in the Chispa Summit Formation at USGS Mesozoic localities D10750 and D10751 (Fig. 1, locs. 48, 49), where the ammonite is associated with Collignoniceras woollgari (Mantell), Tragodesmoceras sp., and Romaniceras sp. In west-central New Mexico, S. coahuilaensis has been found in the upper part of the Rio Salado Tongue of Mancos Shale and in the basal part of the Tres Hermanos Formation at USGS Mesozoic localities D6153, D10606, D11450, D11475, D6804, and D10320 (Fig. 1, locs. 2, 3, 33-36), and questionably at D11264 (Fig. 1, loc. 1).

SPATHITES RIOENSIS Powell Figs. 3M-O, 5A-L, 6A-N, 8 1963. Spathites rioensis Powell, p. 1228, pl. 169, fig. 2, pl. 170, figs. 1-3, 6, 7, text-figs. 5j, 6c-e. 1979. Spathites rioensis Powell: Cobban & Hook, p. 18, pl. 2, figs. 1- 4, p1. 5, figs. 11, 12, p1. 8, figs. 8-13, pl. 11, figs. 1-9, pl. 12, figs. 4-6, text-fig. 9. 1980a. Spathites (Spathites) rioensis Powell: Kennedy, Wright & Hancock, p. 833, text-fig. 8A. 1986. Spathites rioensis Powell: Cobban, p. 81, fig. 3L, M, R-U. Types-Holotype UT 30954 and hypotype USNM 404345 from the Ojinaga Formation at Cannonball Hill east of Cie- neguilla, Chihuahua, Mexico (Fig. 1). Hypotypes USNM 403199, 404346-404355 from the upper part of the Rio Salado Tongue of Mancos Shale and basal part of the overlying Tres Hermanos Formation in central New Mexico. Description-This species is characterized by its adult body chamber that has a concave to flattened venter, rounded ventrolateral shoulder, and smooth or nearly smooth, flattened flanks. The holotype (Powell, 1963, p1. 170, figs. 1, 6, text-fig. 6c) is an internal mold of a fairly large adult 130 mm in diameter, with an umbilical ratio of 0.15. More than one- half of the outer whorl is body chamber, which has a normal aperture. Ribs and tubercles are greatly weakened on the last part of the phragmocone, and only faint umbilical and ventrolateral swellings are present on the older part of the body chamber. The simple suture inked on the holotype (Powell, 1963, pl. 170, fig. 6) is typical of the genus. Lateral and umbilical lobes are fairly narrow and little divided, and the saddles that separate the lobes are broad and bifid with few incisions. Early whorls of S. rioensis, illustrated by Powell (1963, pl. 170, figs. 2, 3, text-fig. 6d) are robust and have whorl sections about as high as wide. Ornament consists of strong, nodate umbilical tubercles that give rise to low, broad, rec-

tiradiate to prorsiradiate ribs. These ribs are separated by one or two secondaries that arise at midflank or higher. All ribs bear nodate to clavate inner ventrolateral tubercles and similar-sized outer ones and then weaken as they cross the venter transversely. On the few specimens at hand from the type locality (Cannonball Hill), all ventrolateral tubercles become clavate near the end of the phragmocone, and the outer ones are slightly stronger and bound a narrow, depressed venter. A very large phragomocone (Powell, 1963, pl. 169, fig. 2) from the type locality suggests dimorphism in this species. Powell did not give its dimensions, but his illustration indicates a specimen still septate at a diameter of about 110 mm. In contrast, the holotype appears to have a diameter of about 65 mm at the base of the body chamber. Spathites rioensis has been collected at several localities in New Mexico. The largest collections are from USGS Mes- ozoic localities D11559 and D11708 in Cibola County and D10643 in Lincoln County (Fig. 1, locs. 7, 8, 45). Locality D11559 has 38 specimens, mostly inner whorls, suitable for measurements of diameter, umbilicus, and number of tubercles. The inner whorls range from slender, involute, weakly to moderately ornamented forms (Fig. 5I J) to robust, less involute, strongly ornamented ones (Fig. 5C—E). In general, the more slender forms have umbilical ratios of 0.14-0.18, and the more robust ones have ratios of 0.190.26 (Fig. 7B). Ribs tend to be weak, straight, rectiradiate, to slighly prorsiradiate. Umbilical tubercles are usually no-date and strong and number 3-7 per half-whorl, averaging 4. Inner ventrolateral tubercles are usually nodate, whereas the outer ones are clavate and slightly stronger. Ventrolateral tubercles number 8-13 per half-whorl, averaging 10. Body chambers are crushed and incomplete. Diameters at the base of body chambers could be determined for only eight specimens; these measurements in millimeters (rounded) are 52, 53, 56, 56, 57, 58, 65, and 99. 15

USGS locality D11708 has 18 specimens suitable for mea- lovi (Shumard) (originally Ammonites swallovii Shumard, 1860: surements, which are much like those from locality D11559. 591) that was more compressed, smoother, and lacked um- Diameters at the base of body chambers are mostly 50-60 mm. bilical tubercles. Specimens that Herrick & Johnson One larger specimen has a measurement of 96 mm. (1900a, p1. 1, figs. 1, 2) regarded as B. swallovi occur in the Only nine specimens are in the collection from locality Rio Puerco valley in great abundance with the variety D10643, but all represent fairly large adults. Diameters in mm puercoensis. These authors also observed that some specimens (rounded) at the base of body chambers, which can be of their variety possessed faint umbilical tubercles and were measured on only four of the specimens, are 84, 92, 94, and 98 transitional to B. swallovi. Shumard's Ammonites swallovii was mm. These adults range from robust forms (Fig. 6M, N) that later designated as the type species of Metoicoceras (Shimer & have trapezoidal whorl sections to slender forms that have Shrock, 1944: 591). rectangular sections. Description—In addition to retaining ornament on the Sutures of S. rioensis (Fig. 8) resemble those of S. coahui- adult body chamber, S. puercoensis is a highly variable species laensis except that the lobes and saddles are a little more that ranges from slender, weakly ornamented forms to robust, incised. strongly ornamented ones. The description by Herrick & Occurrence—Spathites rioensis is abundant at the type lo- Johnson (1900a: 39) is as follows: cality at Cannonball Hill in Chihuahua, Mexico, where Pow- This beautiful species occurs in vast numbers in septaria ell (1963: 1228) recorded 75 specimens from 433 m above concretions of the so-called cephalopod shales in the Rio the base of the Ojinaga Formation. Other ammonites illus- Puerco valley where it is associated with Sphenodiscus len- trated by Powell from this locality include Selwynoceras mex- ticularis, Placenticeras placenta, Pholadomya subventricosa, and other lower Fox Hills species. The typical form as de- icanum (Bose) [Collignoniceras woollgari (Mantell)], Mammites scribed by Shumard is abundant and is accompanied by a [Morrowites] depressus Powell, Neoptychites xetriformis Per- variety or possibly a distinct species characterized by the vinquiere, N. gourguechoni Pervinquiere, and Coilopoceras sp. absence of nodes about the umbilicus, the greater lateral Spathites rioensis is present in only one USGS collection (Fig. compression of the shell and the almost complete absence 1, loc. 47) from Trans-Pecos Texas. Here the species was of the ribs. The paired dorsal nodes, though present, are found with Collignoiceras woollgari and Neoptychites sp. high in the inconspicuous. The sutural pattern is the same except that Boquillas Limestone (Hook & Cobban, 1983: 49). the serration of the lobes is less marked. Individuals with In west-central and western New Mexico, S. rioensis is more prominent ribs and slight development of the umbilical found in concretions of siltstone and very fine-grained nodes indicate the possibility of a transition to the type. The variety may be known as var. puercoensis. Plate I, Figs. 3, sandstone in the basal part of the Tres Hermanos Formation 4. It would seem that the two forms occur together and in septarian limestone concretions in the upper part of wherever the species occurs. the underlying Rio Salado Tongue of Mancos Shale (Fig. 1, Inasmuch as the holotype was not described separately, locs. 6-8, 37-46). Associated ammonites include Morrowites its features depend entirely on the sketch by Herrick & depressus (Powell), Collignoniceras woollgari woollgari (Man-tell), Johnson (reproduced by Hook & Cobban, 1982, fig. 2). The Placenticeras cumminsi Cragin, and Baculites yokoyamai Tokunaga drawing reveals an internal mold of slender adult that had & Shimizu. In some localities a varied bivalve and about one-quarter of a whorl of body chamber preserved. gastropod fauna may also be present (Hook et al., 1983: The specimen apparently had a diameter of about 92 mm 17). Mytiloides subhercynicus (Seitz) and M. hercynicus (Pe- and an umbilicus of 9 mm (0.10). Whorl section of the trascheck) may be present. body chamber is much higher than wide, with divergent flattened flanks and slightly concave venter. Low, clavate ventrolateral tubercles bound the venter on the SPATHITES PUERCOENSIS (Herrick & Johnson) phragmocone and older part of the body chamber. Figs. 3A-L, 9A-C, G-M, 10A-L, 11A-F, 14 Umbilical tubercles are lacking. The large collections from the Rio Puerco valley verify 1900a. Buchiceras swallovi Shumard: Herrick & Johnson, p. 39, pl. 1, figs. 1, 2. that Herrick & Johnson's Buchiceras swallovi and variety puer- 1900a. Buchiceras swallovi var. puercoensis Herrick & Johnson, p. 39, coensis represent a variable population of one species that pl. 1, figs. 3, 4. ranges from compressed, poorly ornamented forms to robust, 1900b. Buchiceras swallovi Shumard: Herrick & Johnson, p. 213, pl. strongly ornamented ones. Specimens that closely resemble 27, figs. 1, 2. the drawing of the holotype of S. puercoensis in lacking 1900b. Buchiceras swallovi var. puercoensis Herrick & Johnson, p. umbilical tubercles on the outer whorl are rare (Fig. 9H-J). 213, pl. 27, figs. 3, 4. Almost all adults have umbilical tubercles on the outer 1917. Metoicoceras puercense [sic] (Herrick & Johnson): Stanton in whorl, although they may be faint on the more slender, Lee, p. 176. weakly ornamented individuals. 1968. Spathites puercoensis (Herrick & Johnson): Dane, Kauffman The largest collection from the Rio Puerco valley, & Cobban, p. 7. 1980a. Spathites (Spathites) puercoensis (Herrick & Johnson): Ken- USGS Mesozoic locality D4020 (Fig. 1, loc. 11), contains nedy, Wright & Hancock, p. 834, pl. 104, figs. 1-5, pl. 70 specimens that consist of complete outer whorls suitable 106, fig. 3, text-fig. 8C. for the determination of two or more of the following 1982. Spathites puercoensis (Herrick & Johnson): Hook & Cobban, measurements: diameter, umbilicus (and ratio to diameter), p. 37, figs. 2-4. whorl breadth (and ratio to diameter), diameter at base of Types—Holotype (Herrick & Johnson, 1900a, pl. 1, figs. 3, body chamber, and number of umbilical and ventrolateral 4; 1900b, pl. 27, figs. 3, 4) from the Mancos Shale of the Rio tubercles per whorl.The specimens range in diameter from Puerco valley northwest of Albuquerque, New Mexico. 30 to 114 mm and have umbilical ratios of 0.09-0.17 (Fig. Hypotypes USNM 404356-404378 from the Mancos Shale and 12B). Body chambers, which are present on many Semilla Sandstone Member of the Mancos in the Rio Puerco specimens, occupy about two-thirds of a whorl (Fig. 10J, valley, Sandoval County, New Mexico. K). Diameters at the base of these body chambers range Remarks—The holotype was apparently housed in the from 49.5 to 88.8 mm (Fig. 13). Hadley Laboratory at the University of New Mexico in Al- An adult that has a diameter of 66.2 mm at the base of the buquerque. The laboratory burned to the ground on May 23, body chamber was taken apart and the inner whorl at a 1910, and all of Herrick & Johnson's material was destroyed diameter of 9.7 mm was examined (Fig. 3D-F). This small (Northrop, 1966: 20). whorl has an umbilical ratio of 0.14 and a breadth to diameter The holotype was defined as a variety of Buchiceras swal ratio of 0.43. The smaller end of the whorl is higher

than wide, with rounded venter and slightly flattened flanks. The larger end of the whorl has a subrectangular section with flattened flanks and narrow, flat venter. Greatest width of the whorl is at the umbilical shoulder. Very weak umbilical and ventrolateral tubercles and poorly defined faint ribs arise at the small end of the whorl and rapidly become distinct at the larger end. Later growth stages of the phragmocone can be seen in many specimens from locality D4020 (Fig. 3A—C). Whorls have a trapezoidal section that is usually higher than wide, with the greatest width at the umbilical shoulder. Flanks and venter are flattened. The specimens range from slender and weakly ornamented to robust and strongly ornamented. Slender specimens tend to be a little more involute than robust ones. Umbilical tubercles, which number 5-9 per whorl, are strong and nodate on robust specimens and weak and bullate on slender ones. Ventrolateral tubercles are clavate; the inner ones are a little weaker than the outer ones. The ventrolateral tubercles number 17-23 per whorl (Fig. 12A) and persist beyond the larger end of the phragmocone. Ribs are broad, flattened, and weak; they arise either from umbilical tubercles or on the outer half of the flank. On robust phragmocones, ribs may cross the venter transversely as low, broad swellings. Body chambers of specimens from locality D4020 have flattened venters, truncated ventrolateral shoulders, and flattened flanks. The umbilicus is narrow and deep, with steep wall and narrowly rounded shoulder; the degree of curvature decreases noticeably toward the aperture. Slender specimens have weak umbilical bullae or none; low, faint inner ventrolateral tubercles or none; and low, outer ventrolateral clavi that may weaken and disappear before reaching the aperture. Robust specimens have conspicuous nodate umbilical tubercles that persist to the aperture; the last one or two usually weaken. Inner and outer ventrolateral tubercles are distinct on the older part of the body chamber, but on the younger part the inner tubercles weaken and disappear, and the outer ones may or may not persist to the aperture. On some robust individuals, inner and outer tubercles merge into low ventrolateral swellings before disappearing on the younger part of the whorl. Ribs are sparse, broad, and faint on the robust body chambers. Apertures at the end of adult body chambers are preserved on many specimens and are nearly all normal (Fig. 10J, K). An exception is one adult 95 mm in diameter that has a slightly flared aperture preceded by a shallow constriction. Sutures of Spathites puercoensis are distinctly pseudoceratitic in that lobes tend to be minutely denticulate and sad-

20 dies little divided (Fig. 14). External lobes of some specimens the Mancos Shale (Dane et al., 1968: 7, 12; La Fon, 1981: are fairly short (Fig. 14F). 710) and in septarian limestone concretions in silty shale Only one specimen out of the 300 at hand is pathologic. transitional into the underlying shale. The fossils occur in This individual (hypotype USNM 400378) has only one row such an abundance that the beds containing them were of ventrolateral tubercles, which are centered at or near the referred to as the "Cephalopod zone" (Herrick, 1900: 338; middle of the venter. Herrick & Johnson, 1900a: 15; Lee, 1917: 195-198) or as the Occurrence—Spathites puercoensis has not been found in "Cephalopod Shale" (Herrick & Johnson, 1900a: 26, 39, 41). Trans-Pecos Texas. The species is abundant only in the Rio Associated ammonites include Hoplitoides sandovalensis Cob- Puerco valley northwest of Albuquerque, New Mexico (Fig. ban & Hook, Herrickiceras costatum (Herrick & Johnson), and 1, locs. 9, 11-31), where the species occurs in sandy cal- Prionocyclus hyatti (Stanton). A recent addition to the fauna is a careous concretions in the Semilla Sandstone Member of fossil crab described by Kues (1980). Some fragments

21 of crushed Spathites from farther west in the Gallup area (Fig. Wage turonien) et des ammonites Carolinus et Fleuriausianus 1, loc. 4) may be S. puercoensis. East of Albuquerque, S. I'état adulte: Societe d'Agriculture, Sciences et Arts d'Angers, puercoensis has been found at one locality (Fig. 1, loc. 32). Mémoires (3), 3: 246-252. Dane, C. H., Kauffman, E. G. & Cobban, W. A., 1968, SemiIla Sandstone, a new member of the Mancos Shale in the south- SPATHITES sp. eastern part of the San Juan Basin, New Mexico: U.S. Fig. 9D-F Geological Survey, Bulletin 1254-F: 21 pp. specimen USNM 404379 from the Carlile Grossouvre, A. de, 1893 [1894], Les ammonites de la craie Type—Figured supérieure, Pt. 2, Paleontologie, of Recherches sur la craie Shale north of Las Vegas, New Mexico. superieure: Carte géobogique detainee de la France Mémoires, Description—An external mold 35.5 mm in diameter with 264 pp., 39 pls. an umbilicus of 5.3 mm (0.15) differs from other slender Herrick, C. L., 1900, Report of a geological reconnaissance in specimens of Spathites in that ribs are strong and inner ven- western Socorro and Valencia Counties, New Mexico: trolateral tubercles are absent. Whorl section is trapezoidal American Geologist, 25 (6): 331-346; New Mexico University with flat flanks and narrow, concave venter sharply bounded Bulletin, 2 (3): 1-17. by conspicuous ventrolateral clavi. Greatest whorl width is at Herrick, C. L. & Johnson, D. W., 1900a, The geology of the Al- the narrowly rounded umbilical shoulder. Broad, rectiradiate buquerque sheet: New Mexico University Bulletin, 2: 1-67; Den- ison University Scientific Laboratories Bulletin, 11 (9): 175-239. ribs arise singly or in pairs from strong, nodate, umbilical Hook, S. C. & Cobban, W. A., 1982, Spathites puercoensis (Herrick tubercles. These ribs are separated by one to three and Johnson)—Common Upper Cretaceous guide fossil in secondaries that arise on the lower half of the flank. All ribs Rio Puerco valley, New Mexico; in Kottlowski, F. E. et al., are flattened a little on the outer part of the flank, where they New Mexico Bureau of Mines & Mineral Resources, Annual bend slightly forward and rise into ventrolateral clavi. The Report, July 1, 1980 to June 30, 1981, pp. 36-39. ribs then cross the venter transversely as low, broad Hook, S. C. & Cobban, W. A., 1983, Mid-Cretaceous molluscan swellings. Ventrolateral clavi on the older part of the whorl sequence at Gold Hill, Jeff Davis County, Texas, with comparison are unusual in that they are doubled. Five umbilical tubercles to New Mexico; in Contributions to mid-Cretaceous paleontology and stratigraphy of New Mexico, part II: New Mexico Bureau of and 20 ventrolateral clavi are present on the complete whorl. Mines & Mineral Resources, Circular 195: 48-54. The poorly preserved suture has a Spathites pattern. Hook, S. C., Molenaar, C. M. & Cobban, W. A., 1983, Stratigraphy Remarks—The specimen was found as float from the and revision of nomenclature of upper Cenomanian to Turonian Codell Sandstone Member of the Carlile Shale. A collection (Upper Cretaceous) rocks of west-central New Mexico; in Con- from a sandstone concretion in the Codell Member at this tributions to mid-Cretaceous paleontology and stratigraphy of locality has Spathites puercoensis and Prionocyclus hyatti. None of New Mexico, part II: New Mexico Bureau of Mines & Mineral the slender specimens of S. puercoensis from the sandstone Resources, Circular 185: 7-28. concretion and none of the slender specimens from the Hyatt, A., 1900, Cephalopoda; in Zittel, K. A. von, Textbook of prolific localities farther west in the Rio Puerco valley palaeontology [1896-1900]: MacMillan, London, pp. 502-604. Jones, T. S., 1938, Geology of Sierra de la Peña and resemble the float specimen in its conspicuous ribbing and paleontology of the Indidura formation, Coahuila, Mexico: lack of inner ventrolateral tubercles. It is possible the spec- Geological Society of America, Bulletin, 49 (1): 69-150. imen is from a slightly higher or lower stratigraphic position Kennedy, W. J., Wright, C. W. & Hancock, J. M., 1980a, Origin, than typical S. puercoensis. In the northern Great Plains region, evolution and systematics of the Cretaceous ammonoid a zone of Prionocyclus percarinatus (Hall & Meek) lies between Spathites; Palaeontology, 23 (4): 821-837. the zones of Collignoniceras woollgari and P. hyatti (Cobban, Kennedy, W. J., Wright, C. W. & Hancock, J. M., 1980b, The 1984: 84), and this zone has been questionably recorded in European species of the Cretaceous ammonite Romaniceras western New Mexico (Hook et al., 1983, fig. 7; Cobban, with a revision of the genus: Palaeontology, 23 (2): 325-362. 1984, fig. 2). A few badly crushed Spathites from the Rio Kennedy, W. J., Lindholm, R. C., Helmold, K. P. & Hancock, J. M., 1977, Genesis and diagenesis of hiatus- and breccia- Salado Tongue of the Mancos Shale of western New Mexico concretions from the mid-Cretaceous of Texas and northern associated with possible P. percarinatus may be the same as Mexico: Sedimentology, 24: 833-844. the float specimen from the Codell Member (Hook et al., Kues, B. S., 1980, A fossil crab from the Mancos Shale (Upper 1983, sheet 1, loc. D7075). Cretaceous) of New Mexico: Journal of Paleontology, 54 (4): Occurrence—USGS Mesozoic locality D10769 (Fig. 1, loc. 862864. 10). Kummel, B. & Decker, J. M., 1954, Lower Turonian ammonites from Texas and Mexico: Journal of Paleontology, 28 (3): 310-319. References La Fon, N. A., 1981, Offshore bar deposits of Semilla Adkins, W. S., 1931, Some Upper Cretaceous ammonites in Sandstone Member of Mancos Shale (Upper Cretaceous), San western Texas: Texas University Bulletin 3101: 35-72. Juan Basin, New Mexico: American Association of Petroleum Amédro, F. & Badillet, G., 1982, Ammonites du Saumurois; in Geologists, Bulletin, 65 (4): 706-721. Robaszynski, F. et al., Le Turonien de la region-type; Saumurois Lee, W. T., 1917 [1918], Geology of the Raton Mesa and other et Touraine, stratigraphie, biozonations, sedimentologie: Centres regions in Colorado and New Mexico; in Lee, W. T. & Knowlton, de Recherches Exploration–Production Elf-Aquitaine, Bulletin, F. H., Geology and paleontology of the Raton Mesa and other 6 (1): 130-138. regions in Colorado and New Mexico: U.S. Geological Survey, Cobban, W. A., 1986, Upper Cretaceous molluscan record from Professional Paper 101: 1-221. Lincoln County, New Mexico: American Association of Petro- Northrop, S. A., 1966, University of New Mexico contributions leum Geologists, Southwest Section, Transactions and Guide- in geology, 1898-1964: University of New Mexico book, 1986 Convention, Ruidoso, New Mexico, pp. 77-89. Publications in Geology, no. 7: 152 pp. Cobban, W. A., 1984, Mid-Cretaceous ammonite zones, Powell, J. D., 1963, Turonian (Cretaceous) ammonites from Western Interior, United States: Geological Society of northeastern Chihuahua, Mexico: Journal of Paleontology, 37 Denmark, Bulletin, 33 (1-2): 71-89. (6): 1217– 1232. Cobban, W. A. & Hook, S. C., 1979 [1980], Collignoniceras woollgari Shimer, H. W. & Shrock, R. R., 1944, Index fossils of North woollgari (Mantell) ammonite fauna from Upper Cretaceous of America: John Wiley & Sons, New York, 837 pp. Western Interior, United States: New Mexico Bureau of Mines & Shumard, B. F., 1860, Descriptions of new Cretaceous fossils Mineral Resources, Memoir 37: 51 pp. from Texas: Academy of Sciences of St. Louis, Transactions, Cobban, W. A. & Hook, S. C., 1983, Mid-Cretaceous (Turonian) 1: 590610. ammonite fauna from Fence Lake area of west-central New Wiedmann, J., 1959 [1960], Le Crétacé superieur de l'Espagne et Mexico: New Mexico Bureau of Mines & Mineral Resources, du Portugal et ses Céphalopodes; in Colloque Crétacé supérieur Memoir 41: 50 pp. français: Societe Savantes Paris Congres, 84th, Dijon, 1959, Sec- Courtiller, [A.], 1860, Description (et figures) de trois nouvelles tion des Sciences, Comptes Rendus, Colloque Crétacé, pp. 709- especes d'ammonites du terrain crétacé des environs de Saumur 764.

The Late Cretaceous ammonite Romaniceras Spath, 1923, in New Mexico

W. J. Kennedy' and W. A. Cobban2

'Department of Geology and Mineralogy, Parks Road, Oxford, OX1 3PR, U.K.; 2U.S. Geological Survey, Mail Stop 919, Box 25046, Federal Center, Denver, Colorado 80225, U.S.A.

Abstract—Romaniceras, represented by R. (Romaniceras) mexicanum Jones and R. (Obiraceras) sp., has been found in two areas of north-central New Mexico. Most specimens, as well as the best preserved ones, occur in silty, calcareous concretions in the Semilla Sandstone Member of the Mancos Shale or a little below that member in the Rio Puerco valley northwest of Albuquerque. Other specimens have been found in septarian limestone concretions in the Blue Hill Member of the Carlile Shale in the Canadian River valley east of Springer. Ammonites associated with Romaniceras in New Mexico include Prionocyclus hyatti (Stanton), Hoplitoides sandovalensis Cobban & Hook, Coilopoceras springeri Hyatt, and Spathites puercoensis (Herrick & Johnson). A middle Turonian age is assigned.

Introduction In the Canadian River valley, Romaniceras occurs in lime- Some remarkable ammonites were collected in 1931 by stone concretions in the upper part of the Blue Hill Member of C. B. Hunt and assistants of the U.S. Geological Survey in the Carlile Shale as well as in the lower part of the overlying the course of mapping the geology and fuel resources of an Code11 Sandstone Member, where the genus was identified area on the west side of the Albuquerque basin. The fossils, as Shuparoceras (Hook & Cobban, 1980, fig. 4). Associated which came from limestone concretions in the Mancos fossils include Prionocyclus hyatti (Stanton) and Coilopoceras Shale, belong to the genera Hoplitoides, Spathites, Prionocyclus, springeri Hyatt. Fossils are generally poorly preserved in- and Romaniceras with the subgenus Obiraceras. All are well pre- asmuch as the concretions are highly septarian. served and uncrushed. Specimens of Hoplitoides in the Hunt Outside New Mexico, Romaniceras is known from the collections were described by Cobban & Hook (1980: 8-11) western interior region only in southeastern Colorado and and those of Spathites are treated by Cobban (1988: this Texas. The Colorado record is based on a crushed fragment volume). The present report is largely based on the Hunt in shaly limestone from the Fairport Chalky Shale Member collections of Romaniceras. of the Carlile Shale at USGS Mesozoic locality D12726 in Fossils described in this report are kept in the National the SE1/4 sec. 26, T20S, R66W, Pueblo County. Romaniceras Museum of Natural History in Washington, D.C., where is fairly common in the Chispa Summit Formation in Trans- they have USNM catalog numbers. Plaster casts of some of Pecos Texas, where (R.) mexicanum Jones occurs in the Prion- the specimens are at the New Mexico Bureau of Mines & ocyclus hyatti Zone and R. (Yubariceras) ornatissimum (Stoliczka) Mineral Resources, Socorro, New Mexico, and in the U.S. occurs in the Collignoniceras woollgari Zone. Romaniceras (R.) Geological Survey's Mesozoic invertebrate fossil collections mexicanum also occurs in the "condensed zone" of Adkins at the Denver Federal Center, Lakewood, Colorado. All (1932: 435) in the upper part of the Eagle Ford Group in the photographs were made by Robert E. Burkholder of the U.S. Austin area (University of Texas and J. P. Conlin Geological Survey. collections).

Stratigraphic position Collection localities Regarding the stratigraphic position of the ammonites in Romaniceras has been found in New Mexico only in the the Rio Puerco valley, Hunt (1936: 43) noted that "About 300 north-central part of the state, where most localities are feet above the top of sandstone no. 3 is a 20-foot zone of clustered in the Rio Puerco valley northwest of Albuquerque limestone concretions. The concretions vary in size, the and in the Canadian River valley east of Springer (Fig. 1). largest being 2 feet in diameter, and commonly contain an The localities, names of collectors, and years of collections abundant and excellently preserved ammonite fauna." are given in Table 1. The prefix D indicates Denver Sandstone no. 3 of Hunt was later named the Twowells Mesozoic locality numbers; the rest are Washington, D.C., Sandstone Tongue of the Dakota Sandstone; the overlying Mesozoic locality numbers. part of the Mancos Shale, which includes the ammonite- Systematic paleontology bearing concretions, was referred to as the main body of the Mancos Shale (Landis et al., 1973). The fossiliferous beds Dimensions are given in millimeters and abbreviations crop out at many places in an extensively faulted area known are as follows: D = diameter, U = umbilical diameter, Wb as the Puerco fault belt (Kelley & Clinton, 1960: 52; Kelley, = whorl breadth, Wh = whorl height, Wb:Wh = ratio of 1977, fig. 19) or zone (Slack & Campbell, 1976; Woodward whorl breadth to whorl height, is = intercostal dimensions, & Callender, 1977: 211). The ammonites occur in silty lime- c = costal dimensions. Suture terminology is that of We- stone concretions that are septarian with dark-brown, light- dekind (1916; see Kullman & Wiedmann, 1970). Reposito- brown, and white calcite veins. Some collections are from the ries of specimens are indicated as follows: UM = Semilla Sandstone Member of the Mancos Shale, and University of Michigan Paleontology Collections, USNM = U.S. National Museum, Washington, D.C.

Order AMMONOIDEA Zittel, 1884 Suborder AMMONITINA Hyatt, 1889 Superfamily ACANTHOCERATACEAE de Grossouvre, 1894 Family ACANTHOCERATIDAE de Grossouvre, 1894 Subfamily EUOMPHALOCERATINAE Cooper, 1978

Genus ROMANICERAS Spath, 1923 Type species—Ammonites deverianus d'Orbigny, 1841: 356, pl. 110, figs. 1, 2; by original designation. Discussion—The type species was revised at length by Kennedy, Wright & Hancock (1980: 332, pl. 39, figs. 7-10, pl. 41, figs. 1-6, pl. 42, figs. 1-7, pl. 43, figs. 1-3, text-figs. 1, 3D, 4, 5). It shows an early stage with smooth, constricted whorls, followed by a stage with collar-ribs to the constrictions, and thereafter an ornamented stage with primary ribs that have nine rows of tubercles (umbilical, lateral, inner and outer ventrolateral, and siphonal) and secondary ribs with no or feeble lateral, inner and outer ventrolateral, and siphonal tubercles. Medium-sized specimens vary in whorl proportions and strength of ribbing and tuberculation, as is normal in such decorated ammonites. Kennedy and others pointed out that there was a sequence in France

25 from Kamerunoceras turoniense (d'Orbigny, 1850) (see revision 1938. Romaniceras mexicanum Jones, p. 121, pl. 7, figs. 1, 6. 1938. in Kennedy & Wright, 1979) to Romaniceras kallesi (Zázvorka, Romaniceras santaanaense Jones, p. 121, pl. 8, figs. 1, 6. 1938. 1958) involving development of nine rows of tubercles Romaniceras toribioense Jones, p. 122, pl. 7, figs. 7, 8. 1959. throughout ontogeny and stabilization of ventral ornament Romaniceras pseudodeverianum (Jimbo): Matsumoto, p. 93 (pars). with rows of siphonal and ventrolateral tubercles equal in 1980. Shuparoceras sp. nov., Kennedy, Wright & Hancock, p. 329, number. Later work has revealed constricted inner whorls in text-fig. 2. Kamerunoceras species, including the type (Cobban & Hook, 1980. Romaniceras (Romaniceras) kallesi (Zázvorka, 1958): 1983: 8, figs. 1, 2), and stabilization of ventral ornament is Kennedy, Wright & Hancock, p. 342 (pars), text-fig. 6. shown by some North American material (Kennedy & Types—Holotype is UM 16928, the original of Jones (1938: Wright, 1979, text-fig. 4). The similarity of the overall shell 121, pl. 7, figs. 1, 6), by original designation. Paratypes are form of K. turoniense to that of R. (R.) kallesi, with which it UM 16098, 16929-16931, from members 2 and 3 of the overlaps in the latter part of its range, is so striking that upper Turonian Indidura Formation north of Tanque Toribio, close affinity cannot be doubted. In France, R. (R.) kallesi is Sierra de Santa Ana, Coahuila, Mexico. Hypotypes are succeeded by Romaniceras (Yubariceras) ornatissimum (Stoliczka, USNM 411600-411610, from the Mancos and Carlile Shales 1865), which has a more massive shell and constricted inner of New Mexico. whorls, just as in R. (R.) kallesi and Kamerunoceras species; Dimensions: ornatissimum differs, however, in having 11 rows of tubercles USNM D Wb Wh Wb:Wh in middle-late growth: umbilical, lateral, outer lateral, inner 411600 c 62.5(100) 23.8(38.1) 26.0(41.6) 0.92 20.0(32.0) and outer ventrolateral, and siphonal. The ontogenetic 411601 c 72.0(100) 28.8(40.0) 31.0(43.1) 0.92 21.3(29.6) development of these tubercles is clearly shown by well- 411604 c 119.0(100) 53.3(44.8) 50.0(42.0) 1.06 37.0(31.1) preserved California material studied by Matsumoto (1959; 411602 c 136.0(100) 69.4(51.0) 61.2(45.0) 1.13 42.0(30.9) especially pl. 29, fig. 4) and other specimens, casts of which is 63.0(—) 60.0(—) 1.05 are before us, together with specimens donated by Professor 411607 c 195(100) 120(61.5) 82.5(42.3) 1.45 77.5(39.7) W. P. Popenoe. They show an early stage with nine rows of 104(—) 76(—) 1.37 tubercles and constrictions succeeded by later stages in 411608 c 293(100) 132(45.0) 109(37.2) 1.21 102.5(34.9) which an outer lateral row develops giving the 11 rows. We 125(—) 109(—) 1.15 411609 c 345(100) 156(45.2) 141(40.9) 1.11 115(33.3) see no reason other than to regard Yubariceras as a subgenus 134.5(—) 132(—) 1.01 of Romaniceras. Description—The early whorls to a diameter of approx- Shuparoceras Matsumoto, 1975 (p. 110, type species Shu- imately 15 mm are evolute and rounded in section. The most paroceras yagii Matsumoto, 1975: 110, pl. 12, fig. 1, text-fig. 3) prominent ornament is four deep, narrow constrictions per was characterized by, among other features, the presence of half-whorl, prorsiradiate and straight on the inner and middle constrictions and nine rows of tubercles (umbilical, lateral, flank and projected forwards over the ventrolateral shoulder, inner and outer ventrolateral, and siphonal). Matsumoto crossing the venter in a broad convexity (Figs. 6A, 7B). regarded it as closely allied to the subgroup of Calycoceras These constrictions are flanked by adapical and adoral choffati (Kossmat, 1897: 12, pl. 4, fig. 1) of the Cenomanian, collared ribs which bear feeble umbilical bullae and from which it differed in having a lateral tubercle; it was ventrolateral and siphonal nodes; the latter also occur believed to be Turonian in age. The present material referred between constrictions. This constricted stage is followed by to R. (Romaniceras) mexicanum Jones, 1938, includes variants rapid acquisition of ornament (Figs. 5A-F, 6A-D, 7A-B). that have all the characters of Shuparoceras (e.g. Fig. 7F-G) and Coiling remains evolute, and the umbilicus is of moderate indeed, one of our specimens was referred to the genus by depth with flattened wall. The whorl section varies from Kennedy, Wright & Hancock (1980, text-fig. 2; see Fig. 8C- slightly compressed (Fig. 2A) to slightly depressed; the latter E herein). We conclude that Shuparoceras is no more than a is most common. The flanks are flattened and convergent in feebly ribbed variant of Romaniceras and regard the former as a intercostal section, with a broadly rounded venter. The costal synonym of the latter. section is compressed polygonal, with a whorl breadth to A final genus to consider in this discussion of Romaniceras and height ratio of 0.92 to 1.13, the greatest breadth being at the its allies is Neomphaloceras Matsumoto & Obata, 1982, with lateral bullae. Between diameters of 50 and 100 mm, the Yubariceras pseudomphalum Matsumoto (1975: 146, pl. majority of specimens bear dense, crowded ribs. Small 22, fig. 1) as type species of uncertain, but probably Turon- umbilical bullae that number 10-22 per whorl give rise to ian age. Matsumoto & Obata (1982: 71) also included Yu- low, straight primary ribs, either singly or in pairs, while bariceras fujishimai Matsumoto (1975: 148, pl. 22, fig. 2, pl. additional intercalated ribs are inserted low or high on the 23, fig. 3, text-fig. 17), undoubtedly an upper Turonian flank to give up to 50 ribs in total per whorl. There may be species, in the genus and suggested that Yubariceras japonicum occasional feeble constrictions (Fig. 6C). The ribs are Matsumoto, Saito & Fukada (1957: 31, pl. 8, fig. 2, text- straight and prorsiradiate on the flank, and bear a conical figs. 11, 12; see also Matsumoto, 1975: 139, pl. 19, figs. 2, lateral tubercle below mid-flank on the primaries and on 3, pl. 21, fig. 2, text-figs. 13, 14) might also belong there. some of the longer secondaries; all ribs bear a conical inner They diagnose Neomphaloceras as very similar to ventrolateral tubercle connected to a feebly clavate outer Euomphaloceras in shell form, ornamentation, and suture, but ventrolateral one by a broadened and strengthened distinguish it in having extra rows of tubercles. The type prorsiradiate rib. A weakened rib projects slightly forward species of Neomphaloceras has nine rows of tubercles on the and links to a clavate siphonal tubercle. At this stage in primary ribs, with secondary ribs and short ventral ribs, so development, the umbilical and outer ventrolateral tubercles that there are more ventrolateral and siphonal than lateral are strongest, and the lateral one weakest (Figs. 7C-D, 8A-E). and umbilical tubercles per whorl. This is a character shown Beyond 106 mm in diameter the whorls become by certain of the present specimens of Romaniceras (e.g. Fig. progressively more massive, depressed, and trapezoidal in 8B), although to a lesser degree than in the Japanese section (Fig. 7D). Rib density decreases to 36-38 per whorl at species; Neomphaloceras seems to us to be at most a subgenus a diameter of 120-150 mm, by the progressive elimination of of Romaniceras, and possibly not even that. secondary ribs. The lateral tubercles increase in relative size and dominate the tuberculation, while the inner ventrolateral ROMANICERAS (ROMANICERAS) MEXICANUM Jones, 1938 ones remain conical and stronger than the clavate outer Figs. 2, 3, 5, 6A-D, G, 7-10 ventrolateral and siphonal tubercles (Fig. 8D). The outer 1938. Romaniceras adkinsi Jones, p. 120 (pars), p1. 8, figs. 4, 5. whorl of the adult phragmocone has an even more

The body chamber extends for just over half a whorl (Fig. 5G), with possible microconchs just over 300 mm in diameter and an adult macroconch with incomplete body chamber nearly 380 mm in diameter. The whorl section is depressed and massive. The umbilical seam egresses, umbilical bullae decline, and secondary ribs are lost; lateral tubercles persist. Inner ventrolateral tubercles develop into massive horns on the older part of the body chamber (Fig. 9), but seem to weaken towards the last-formed section. The horns have a characteristic asymmetric profile in side view, with a long, gently inclined adapertural side and steeper adapical one; they project outwards from the venter, which is concave at the beginning of the body chamber, the concavity decreasing towards the aperture as a broad bar-like ventral rib develops and strengthens progressively. External suture with broad, bifid E/L; narrow, symmet- rical L; and broad, bifid L/U2 (Fig. 3). Discussion—Most specimens show finely and evenly ribbed early and middle growth stages, but there is a range of variation. At one extreme is USNM 411605 (Fig. 7F-G),

depressed, trapezoidal section (Fig. 2C) with 13-16 primary ribs and a total of 24-26 ribs at the ventrolateral shoulder (Figs. 5G, 6G, 9, 10). The bullae remain strong and give rise to broad, blunt prorsiradiate primary ribs with a massive conical to somewhat radially elongate lateral tubercle. All ribs bear a massive inner ventrolateral tubercle, but there is a progressive decline of first the siphonal tubercles and then the outer ventrolateral clavi, so that at the end of the phragmocone the venter is slightly concave in costal section, with faint swellings only marking the site of these tubercles (Fig. 10A). Specimens are adult at phragmocone diameters of 250, 190, and 195 mm; a fourth large phragmocone is just over 250 mm in diameter. It is likely that the larger phragmocones are those of macroconchs (Figs. 9, 10A) and the smaller of microconchs (Figs. 5G, 6G), but the sample is too small for certainty on this point.

33 where there is a decline in flank ornament in middle Occurrence-Middle Turonian Prionocyclus hyatti Zone, growth, leaving prominent umbilical bullae and inner Coilopoceras springeri Subzone in New Mexico and at Chispa ventrolateral tubercles plus weakened outer ventrolateral Summit, Jeff Davis County, Trans-Pecos Texas; Eagle and siphonal tubercles, although nuclei are well ornamented Ford "condensed zone" of the Austin area, Travis County, (Fig. 7E). USNM 411604 (Fig. 8A-B) links this to the more Texas. The type material from Coahuila, Mexico, is common variants, showing renascent distant flank imprecisely placed within the Turonian. ornament at diameters above 150 mm. At the other extreme is USNM 411606 (Fig. 7C-D), with coarse ribbing and tuberculation throughout. We take these differences to Subgenus OBIRACERAS Matsumoto, 1975 be normal intraspecific variation. The holotype of Romaniceras mexicanum (Jones, 1938: 121, Type species-Obiraceras ornatum Matsumoto, 1975: 151, pl. pl. 7, figs. 1, 6), from the Turonian of Sierra de Santa Ana, 23, fig. 1, text-fig. 18. Coahuila, Mexico, is very poorly preserved, but shows, at a Discussion-Matsumoto (1975: 150) proposed Obiraceras diameter of 150 mm, an estimated 15-16 umbilical bullae for multituberculate Turonian acanthocerataceans that have giving rise to strong primary ribs with a much stronger primary ribs with nine rows of tubercles (umbilical, lateral, lateral tubercle and a strong outer ventrolateral one. The inner and outer ventrolateral, and siphonal) and secondaries total rib density is 12 per half-whorl. All these characters with or without feeble lateral, inner and outer ventrolateral, match with our material, and as first revising authors, we and siphonal tubercles in early growth; inner and outer select Jones' name for the species, although the ventrolateral tubercles show doubling in middle growth. mexicanum The presence of constricted inner whorls reveals that Obi- holotype is appallingly abraded and does not show the inner raceras belongs to the Euomphaloceratinae. Kennedy, Wright whorls. The type series of Romaniceras coahuilense Jones & Hancock (1980) noted that the genus was comparable to (1938: 118, pl. 6, fig. 1, pl. 7, fig. 5) consists of equally worn other Romaniceras/Yubariceras species except for the doubling and battered specimens. That species comes from the same of tubercles, and noted that such doubling of tubercles was horizon and locality as mexicanum. The holotype is much shown by Nigerian material referred to Romaniceras uchaux- coarser and distantly ribbed, and has 11 rows of tubercles iense Collignon, 1939 (which they thought to be a synonym (not eight as stated by Jones), being a Yubariceras, as is the of R. deverianum). The present specimens would, on all other slender R. kanei Jones (1938: 120, pl. 8, figs. 2, 7, 8, pl. 9, fig. characters but doubling of the ventrolaterals, be inseparable 6). Romaniceras adkinsi Jones (1938: 120, pl. 8, figs. 4, 5) is from Romaniceras, and treatment as subgenus of that genus is also based on a very worn and battered holotype with nine followed here. rows of tubercles, the lateral row becoming increasingly prominent with growth; it is a possible synonym of mexicanum and comes from the same locality as the types of ROMANICERAS (OBIRACERAS) sp. that species. The holotype of Romaniceras santaanaense Jones Figs. 4A, B, 6E, F (1938: 121, pl. 8, figs. 1, 6), from the same locality as the types of mexicanum and adkinsi, is probably a worn example Types-Figured specimens USNM 411611, 411612. of the common variant amongst our material, with well- Description-Two fragmentary specimens are North developed lateral tubercles. Romaniceras toribioense Jones American representatives of Obiraceras. USNM 411611 is a (1938: 122, pl. 7, figs. 7, 8), characterized according to Jones wholly septate fragment with a maximum preserved whorl by its small size and flexuous ribs, seems to be no more height of 49 mm and a whorl breadth to height ratio of 0.82; than a worn example of R. mexicanum and is from the same its whorls are depressed, with greatest breadth at the lateral locality. tubercle (Fig. 4B). The inner flanks are broadly rounded, the Romaniceras loboense Adkins (1931: 44, pl. 2, figs. 1, 21, pl. outer flanks flattened and convergent, the ventrolateral 3, fig. 5) is a R. (Yubariceras) with 11 rows of tubercles per shoulders broadly rounded, and the venter flattened in in- whorl, as is Romaniceras cumminsi Adkins (1931: 43, pl. 3, fig. tercostal section. Prominent umbilical bullae give rise to 6), as pointed out by previous authors (Matsumoto, 1959; broad, blunt prorsiradiate primary ribs, all of which develop Kennedy et al., 1980); both are synonyms of R. (Yubariceras) a strong, pointed lateral tubercle (damaged in most cases). ornatissimum (Stoliczka, 1865: 75, pl. 40). Occasional intercalated ribs arise around mid-flank without Kennedy, Wright & Hancock (1980) referred one of the developing a lateral tubercle. All ribs bear a strong, conical present specimens to Shuparoceras sp. nov. (loc. cit., text-fig. inner ventrolateral tubercle; a broad, low rib extends to a 2), but it is now seen to be an immature individual of R. strong ventral clavus with two much weaker clavi between mexicanum (for our current view of Shuparoceras see above). (Fig. 6F). The rib effaces markedly over the venter, leaving a These same authors illustrated a juvenile with constricted broad, effectively smooth zone on either side of a row of inner whorls as a Romaniceras kallesi (Zázvorka, 1958). It is siphonal clavi only slightly weaker than the ventrolateral again a specimen of R. mexicanum; during middle and later ones. There are thus a total of nine rows of major tubercles growth R. kallesi retains evolute coiling with slender whorls, and four rows of weak tubercles. The second specimen is never developing the massive, coarsely ribbed adult form of poorly preserved, but shows the same style of ornament Romaniceras mexicanum and reaching maturity at less than half with relatively strong lateral tubercles. the size of our material (Kennedy et al., 1980): 342, pl. 44, Sutures with broad bifid E/L, narrower L, and broad figs. 1-3, pl. 45, figs. 3-7, non 1, 2, pl. 47, figs. 1-4, text-fig. bifid L/U2 (Fig. 4A). 6). The type species of Romaniceras, R. deverianum (d'Orbigny, Discussion-The type species of Obiraceras has the same 1841: 346, pl. 110, figs. 1, 2; see Kennedy et al., 1980: 332, pattern of ribbing and tuberculation as the present pl. 39, figs. 7-10, pl. 41, figs. 1-6, pl. 42, figs. 17, pl. 43, figs. material, but has only a slightly depressed whorl section in 1-3, text-figs. 1, 3D, 4, 5), has a similar smooth constricted middle growth, becoming compressed at a diameter when initial stage as in R. mexicanum, but develops umbilical bullae the New Mexico specimens are very depressed. There is that project into the umbilicus in middle growth, whereas too little material to determine the significance of these adults are slender and do not develop the massively ribbed differences. Specimens from the Turonian of Nigeria and tuberculate adult stage seen in the present material. The referred to Romaniceras uchauxiense Collignon by Reyment adults in the present collection resemble to a degree adult (1955: 46, pl. 9, fig. 2) show doubling of ventral tubercles Romaniceras (Yubariceras) ornatissimum (Stoliczka, 1865: 75, pl. and closely resemble our specimens. 40), but that species has 11 rows of tubercles in all but the Occurrence-Middle Turonian Prionocyclus hyatti Zone, latest growth stages. Coilopoceras springeri Subzone of New Mexico (Fig. 1). 34

References reich-Ungarns und des Orients, 1895, 9: 97-203 (1-107), pls. 1525 (1-11); 1897, 11: 1-46 (108-153), pls. 1-8 (12-19); 1898, 12: Adkins, W. S., 1931, Some Upper Cretaceous ammonites in 89152 (154-217), pls. 14-19 (20-25). western Texas: Texas University Bulletin 3101: 35-72. Kullmann, J. & Wiedmann, J., 1970, Significance of sutures in phy- Adkins, W. S., 1932, The geology of Texas, Part 2, The Mesozoic logeny of Ammonoidea: University of Kansas Paleontological systems in Texas: Texas University Bulletin 3232 (v. 1): 239- Contributions, Paper 47: 32 pp. 518. (published 1933) Landis, E. R., Dane, C. H. & Cobban, W. A., 1973, Stratigraphic Cobban, W. A., 1988, The Late Cretaceous ammonite Spathites Kum- terminology of the Dakota Sandstone and Mancos Shale, west- mel & Decker in New Mexico and Trans-Pecos Texas; in Contri- central New Mexico: U.S. Geological Survey, Bulletin 1372-J: butions to Late Cretaceous paleontology and stratigraphy of New 44 pp. Mexico, Part 2: New Mexico Bureau of Mines & Mineral Re- Matsumoto, T., 1959, Upper Cretaceous ammonites of sources, Bulletin 114. California, Pt. 1: Kyushu University, Faculty of Science, Cobban, W. A. & Hook, S. C., 1980, The Upper Cretaceous (Tu- Memoirs (D, Geology), 8 (4): 97-171. ronian) ammonite family Coilopoceratidae Hyatt in the Western Matsumoto, T., 1975, Additional acanthoceratids from Hokkaido Interior of the United States: U.S. Geological Survey, Professional (Studies of the Cretaceous ammonites from Hokkaido and Paper 1192: 28 pp. Saghalien-XXVIII): Kyushu University, Faculty of Science, Cobban, W. A. & Hook, S. C., 1983, Mid-Cretaceous (Turonian) Memoirs (D, Geology), 22 (2): 99-163. ammonite fauna from Fence Lake area of west-central New Matsumoto, T. & Obata, I., 1982, Some interesting acanthocera- Mexico: New Mexico Bureau of Mines & Mineral Resources, taceans from Hokkaido (Studies of Cretaceous ammonites Memoir 41: 50 pp. from Hokkaido-XLII): National Science Museum Bulletin (C, Collignon, M., 1939, Fossiles cénomaniens et turoniens du Menabe Geology and Paleontology), 8 (2): 67-91; Tokyo. (Madagascar): Madagascar, Service des Mines, Annales Matsumoto, T., Saito, R. & Fukada, A., 1957, Some acanthoceratids géologigues, no. 10: 59-105. from Hokkaido (Studies on the Cretaceous ammonites from Cooper, M. R., 1978, Uppermost Cenomanian-basal Turonian Hokkaido and Saghalien-XI): Kyushu University, Faculty of ammonites from Salinas, Angola: South African Museum, Science, Memoirs (D, Geology), 6 (1): 1-45. Annals, 75 (5): 152 pp. Orbigny, A. d', 1840-42, Paleontologie francaise: Terrains Grossouvre, A. de, 1894, Les ammonites de la craie superieure, crétacés, v. 1, Cephalopodes, pp. 1-120 (1840); pp. 121-430 pt. 2, Paleontologie, of Recherches sur la craie supérieure: (1841); pp. 431-662 (1842); 148 + 3 pls.: V. Masson, Paris. Carte geologique detainee de la France, Mémoires, 264 pp. Orbigny, A. d', 1850, Prodrome de paleontologie stratigraphique (misdated 1893) universelle des animaux mollusques et rayonnes, v. 2: V. Hook, S. C. & Cobban, W. A., 1980, Some guide fossils in Upper Masson, Paris, 428 pp. Cretaceous Juana Lopez Member of Mancos and Carlile Reyment, R. A., 1955, The Cretaceous Ammonoidea of southern Shales, New Mexico; in Kottlowski et al., New Mexico Bureau Nigeria and the southern Cameroon: Nigeria Geological of Mines & Mineral Resources, Annual Report, July 1, 1978 to Survey, Bulletin 25: 112 pp. June 20, 1979, pp. 38-49. Slack, P. B., Campbell, J. A., 1976, Structural geology of the Rio Hunt, C. B., 1936, The Mount Taylor coal field, Part 2 of Geology and fuel resources of the southern part of the San Juan Basin, Puerco fault zone and its relationship to central New Mexico New Mexico: U.S. Geological Survey, Bulletin 860-B: 31-80. tectonics; in Tectonics and mineral resources of southwestern Hyatt, A., 1889, Genesis of the Arietidae: Smithsonian Contribu- North America: New Mexico Geological Society, Special Publi- tions to Knowledge, 26 (637): 238 pp.; Harvard Museum of cation 6: 46-52. Comparative Zoology, Memoirs, 16 (3): 238 pp. Spath, L. F., 1923, On the ammonite horizons of the Gault and Jones, T. S., 1938, Geology of Sierra de la Pena and paleontology contiguous deposits; in Great Britain, Geological Survey sum- of the Indidura formation, Coahuila, Mexico: Geological mary of progress for 1922: 139-149. Society of America, Bulletin, 49 (1): 69-150. Stoliczka, F., 1864-66, The fossil Cephalopoda of the Cretaceous Kelley, V. C., 1977, Geology of the Albuquerque Basin, New rocks of southern India (Ammonitidae): India Geological Mexico: New Mexico Bureau of Mines & Mineral Resources, Survey, Memoirs, Palaeontologia Indica, pp. 41-216. Memoir 33: 60 pp. Wedekind, R., 1916, Ober Lobus Suturallobus und Inzision: Zen- Kelley, V. C. & Clinton, N. J., 1960, Fracture systems and tralblatt fur Mineralogie, Geologie und Palaontologie (B), 1916 tectonic elements of the Colorado Plateau: University of New (8): 185-195. Mexico Publications in Geology, no. 6: 104 pp. Woodward, L. A. & Callender, J. F., 1977, Tectonic framework Kennedy, W. J. & Wright, C. W., 1979, On Kamerunoceras Reyment, of the San Juan Basin; in San Juan Basin III: New Mexico 1954 (Cretaceous: Ammonoidea): Journal of Paleontology, 53 (5): Geological Society, Guidebook 28: 209-212. 1165-1178. Zázvorka, V., 1958, Acanthoceras kallesi n.sp. (Ammonoidea) ze Kennedy, W. J., Wright, C. W. & Hancock, J. M., 1980, The Eu- spodniho turonu na Bile Hore v Praze (Stredni Cechy) a Acan- ropean species of the Cretaceous ammonite Romaniceras with a thoceras sharpei n.sp. z anglické kridy: Casopis Národniho Musea revision of the genus: Palaeontology, 23 (2): 325-362. v Praze, 127: 38-45. Kossmat, F., 1895-98, Untersuchungen fiber die südindische Krei- Zittel, K. A., 1884, Handbuch der Paläontologie, Bd. 1, Abt. 2, deformation: Beitrage zur Paläontologie und Geologie Öester- Liefg. 3, Cephalopoda: R. Oldenbourg, Leipzig, pp. 329-552. 35

Middle Cenomanian (Late Cretaceous) molluscan fauna from the base of the Boquillas Formation, Cerro de Muleros, Dona Ana County, New Mexico

W. J. Kennedy,' W. A. Cobban,2 and S. C. Hook3

'Department of Geology and Mineralogy, Oxford University, Oxford, U.K.; '2U.S. Geological Survey, Denver, Colorado, U.S.A.; 3Texaco Exploration and Production Technology Division, Houston, Texas, U.S.A.

Abstract—A thin bed of calcarenitic and coquinoidal limestone forms the base of the Boquillas Formation and rests disconformably on the lower Cenomanian Buda Limestone. This bed contains a fauna that indicates the zone of Acanthoceras amphibolum Morrow. The following stratigraphically important molluscan fossils (chiefly ammonites) are described and illustrated: Desmoceras (Pseu- douhligella) sp., Moremanoceras straini sp. nov., Acanthoceras amphibolum Morrow, Cunningtoniceras cf. johnsonianum (Stephenson), Paracompsoceras landisi Cobban, Tarrantoceras sellardsi (Adkins), Anisoceras cf. plicatile (J. Sowerby), Turrilites acutus Passy, Ostrea beloiti Logan, and Inoceramus arvanus Stephenson.

Introduction Washington, D.C. R. E. Burkholder, U.S. Geological Survey, Cerro de Muleros, also known as Cerro de Cristo Rey, is took the photographs and prepared many of the specimens. approximately 8 km (5 mi) northwest of downtown El Paso, Kennedy acknowledges the financial support of the Natural Texas, in part in Dona Ana County, New Mexico, and in part Environment Research Council and Royal Society, and the in Chihuahua, Mexico. The main mass of the uplift is a technical assistance of the staff of the Geological Collections, hypabyssal plutonic complex of early Tertiary age that has Oxford University Museum and Department of Earth deformed the surrounding Lower and Upper Cretaceous Sciences, Oxford. rocks. The general geology of the area was described by Lovejoy (1976), who provided a detailed geologic map and Systematic paleontology reviewed early work on the region. The Cretaceous succession was first studied by Bose (1910), who recognized 11 All dimensions are given in millimeters, with D = di- units on the basis of lithology and fauna. Strain (1968, 1976) ameter, Wb = whorl breadth, Wh = whorl height, Wb:Wh reviewed Bose's work in detail and proposed a series of = whorl breadth to height ratio, and U = umbilical di- lithostratigraphic units. The material described below came ameter. Figures in parentheses are dimensions as a per- from the base of unit 11 of Bose, referred to as the Boquillas centage of the diameter; c = costal, is = intercostal Formation by Strain in 1968, although he subsequently dimensions. Suture terminology is that of Wedekind (Strain, 1976: 82) suggested that Ojinaga Formation or (1916) as propounded by Kullmann & Wiedmann (1970). Chispa Summit Formation might be more appropriate; Repositories of specimens: TMM, Texas Memorial Mu- taxonomy of the name is of no importance in the present seum, University of Texas at Austin; USNM, National Mu- context, and we use Boquillas, following Strain (1968). This seum of Natural History, Washington, D.C. unit rests with marked disconformity on the underlying Buda Limestone and crops out only intermittently. Bose (1910) Order AMMONOIDEA Zittel, 1884 gave a thickness of 110 m (360 ft) for his unit 11. Suborder AMMONITINA Hyatt, 1889 The fauna described herein came from a few centimeters Superfamily DESMOCERATACEAE Zittel, 1884 thick bed of coquinoidal and calcarenitic limestone at the Family DESMOCERATIDAE Zittel, 1885 base of the formation. These fossils are of much interest Subfamily DESMOCERATINAE Zittel, 1895 because the nearest large fauna of comparable age (zone of Genus MOREMANOCERAS Cobban, 1972 Acanthoceras amphibolum) is from some 400 km (250 mi) farther north in New Mexico (Cobban, 1977a, table 1). All Type-species—Tragodesmoceras scotti Moreman, 1942: fossils came from a single locality about 1.2 km north of 208, pl. 33, fig. 8, text-fig. 2d; by original designation. Cerro de Cristo Rey in the center of the N1/2 SW1/4 sec. 9, Discussion—Moremanoceras was originally proposed as a T29S, R4E, Dona Ana County. The fossils were collected subgenus of Desmoceras Zittel, 1884 (Cobban, 1971: 5), by W. S. Strain, D. V. LeMone and students (University of from which it differs chiefly in having a simpler suture with Texas at El Paso), J. D. Powell (Grand Junction, Colorado), much broader L and short auxiliary lobes. The type species is E. R. Landis and W. A. Cobban (U.S. Geological Survey, from the upper Cenomanian Sciponoceras gracile Zone, but Denver, Colorado), and S. C. Hook (Texaco Research Cen- subsequent work has revealed a succession of species, first ter, Houston, Texas). appearing in the middle Cenomanian, some with distinct Acknowledgments—Prof. David V. LeMone, University flank and ventrolateral ribs in early growth and widely sep- of Texas at El Paso, kindly transferred the figured UTEP arated flared ribs in later growth (as in the type species) and specimens to the National Museum of Natural History, some also with a siphonal ridge in middle and late 36 growth. These forms are restricted to the Western Interior genus. Desmoceras (Pseudouhligella) elgini Young (1958: 292, pl. 39, region and are so far removed from Desmoceras in both su- figs. 4-20, 24, 25, 30, 31, text-fig. 1a-e) is much more ture and ornament that in recent years Moremanoceras has compressed when young, develops thickened collar-ribs at been considered a full genus (e.g. Cobban, 1984a: 79-81, only 15 mm diameter and, when mature, has distant flank 1984b: 19, 1986: 81). We further refer Desmoceras (Pseudouhl- and ventrolateral ribs, and never develops a keel. More- igella) elgini Young, 1958 (p. 292, pl. 39, figs..4-20, 24, 25, 30, manoceras straini of the amphibolum Zone is succeeded, in the 31, text-fig. 1a-e), originally described from the base of the Calycoceras canitaurinum Zone of the Western Interior, by an Boquillas Formation of Trans-Pecos Texas, to Moremanoceras. undescribed species in which the keel is sharper and present The suture (Young, 1958, text-fig. la) has a simple, broad, from a much earlier ontogenetic state, and concave ribs are trifid L as in the present genus, and adult topotypes before well developed over the ventrolateral shoulders. us develop distant bar-like ribs as in other members of the Moremanoceras scotti (Moreman, 1942: 208, pl. 33, fig. 8, text- Moremanoceras lineage. fig. 20) (see Cobban, 1971: 6, pl. 2, figs. 1-23, text-figs. 35), from the Sciponoceras gracile Zone of Texas and the Western MOREMANOCERAS STRAINI, new species Interior, lacks a siphonal keel/ridge at any stage of de- Fig. 1a-g, i-t velopment, and has a tiny umbilicus; it also has regular, distant collar-ribs that extend to the umbilical shoulder and 1955. Desmoceras? sp.: Stephenson, p. 58, pl. 4, figs. 12, 13. 1977a. are prorsiradiate on the flank rather than biconcave. Desmoceras (Pseudouhligella) aff. D. japonicum Yabe: Cobban, p. 22, pl. 11, figs. 1-6, 9, 10. Occurrence-Middle Cenomanian Acanthoceras amphibolum 197Th. Desmoceras (Pseudouhligella) aff. D. japonicum Yabe: Cobban, Zone of the Western Interior and Trans-Pecos Texas; fig. 4a-e. Cloice Member of the Lake Waco Formation of Adkins & Types-Holotype USNM 416051, figured paratypes USNM Lozo (1951) at Cloice Branch, McLennan County, Texas; 416052-416059, unfigured paratypes USNM 416060. Tarrantoceras rotatile concretions in lower part of Eagle Ford Etymology-Named in honor of the late William S. Strain, Group of Johnson County, Texas. former Professor Emeritus at the University of Texas at El Paso, for his research on the Cretaceous stratigraphy of the Genus DESMOCERAS Zittel, 1884 Cerro de Muleros area. Prof. Strain also collected several of Subgenus DESMOCERAS (PSEUDOUHLIGELLA) Matsumoto, 1938 the fossils illustrated in this report. Type species-Desmoceras dawsoni Whiteaves var. japonica Yabe, Material-32 specimens. Dimensions: 1904: 35, pl. 5, fig. 3a, b; by subsequent designation USNM D Wb Wh Wb:Wh (Matsumoto, 1938). 416058 36.9(100) 16.9(45.8) 6.0(16.3) 416051 56.5(100) 21.3(37.7) 25.0(44.2) 0.85 11.4(20.2) 416052 55.0(100) 23.9(43.3) 26.4(48.0) 0.91 9.0(16.4) DESMOCERAS (PSEUDOUHLIGELLA) sp. Diagnosis-Moremanoceras with compressed to slightly Fig. lu, v depressed whorl section, smooth with biconcave growth 1977a. Desmoceras (Pseudouhligella) sp.: Cobban, p. 22, pl. 4, fig. 7. lines on shell and periodic biconcave constrictions on in- Material-One specimen only, USNM 416061. ternal mold that form acute chevrons on venter. Venter Description-The specimen, an internal mold crushed on initially rounded, but develops a blunt rounded keel at ma- one side, has a diameter of 36 mm and an umbilical ratio of turity, when constrictions appear accompanied by blunt 0.24. Its whorl section is compressed, flat-sided with an adapical ventrolateral collar ribs. arched, rounded venter. The umbilicus is shallow with a Description-Coiling involute, with 60% of previous whorl narrowly rounded umbilical shoulder. A conspicuous con- covered. Umbilicus small (16-20% of diameter), with vertical striction is present at a diameter of 31.5 mm; it is narrow wall. Umbilical shoulder narrowly rounded, inner flanks and convex on the inner to mid-flank, then deepens and flattened, subparallel, outer flanks converging to arched, broadens and becomes concave on the outer flank before rounded venter in early growth stages becoming raised into a projecting forward and narrowing to form an acute chevron blunt keel flanked by shallow depressions in later growth over the venter. A broad, coarse, blunt collared rib is stages. Shell surface bears faint, flexuous prorsiradiate growth present on the adapical side and is strengthened into a striae, feebly concave on the inner flank, feebly convex across bulla-like development on the ventrolateral shoulder. the middle of the flanks, and concave on the outer flank Sutures are not preserved. where they are projected forwards over the ventrolateral Discussion-The specimen probably represents the inner shoulder to form a narrow linguoid peak over the venter. whorls of the same species that was illustrated from this Parallel to these are periodic constrictions, five to six per zone farther northwest in Sandoval County, New Mexico whorl, weak on the shell exterior but stronger on the mold. (Cobban, 1977a: 22, pl. 4, fig. 7). The Sandoval specimen is These constrictions deepen and broaden markedly across the a phragmocone 100 mm in diameter that has flat flanks, ventrolateral shoulder, but narrow and attenuate before conspicuous constrictions, and a complex suture. reaching the line of the mid-venter. A collar rib develops adapically to these constrictions in most cases, and is most conspicuous on the ventrolateral shoulder. Superfamily ACANTHOCERATACEAE de Grossouvre, 1894 Family ACANTHOCERATIDAE de Grossouvre, 1894 Discussion-The 32 specimens from Cerro de Muleros Subfamily ACANTHOCERATINAE de Grossouvre, 1894 reveal the development of the species from 9.5 mm in diameter to a whorl height of 33 mm. The early whorls (Fig. Genus CUNNINGTONICERAS Collignon, 1937 1f, g, i-k) are flat-sided and resemble very much Desmoceras sensu stricto, although the later development of a keel (Fig. Type species-Ammonites cunningtoni Sharpe, 1855:35, pl. 15, 1n, s) separates them from all described species of that fig. 2; by original designation.

CUNNINGTONICERAS cf. IOHNSONIANUM (Stephenson, 1955) 1953. Acanthoceras hazzardi Stephenson, p. 201, pl. 48, figs. 1, 2, Fig. 2o, p pl. 49, fig. 4. (1952 imprint) 1955. Euomphaloceras alvaradoense (Moreman): Stephenson, pl. 63, 1955. Acanthoceras johnsonianum Stephenson, p. 58, pl. 4, figs. 14- pl. 7, figs. 1-9. 17. 1960. Acanthoceras amphibolum Morrow: Matsumoto, p. 41, text-fig. 1955. Euomphaloceras lonsdalei (Adkins): Stephenson, p. 62 (pars), 5b-d. pl. 6, figs. 9-20 only. 1960. Acanthoceras hazzardi Stephenson: Matsumoto, p. 41, text-fig. Type—USNM 108846, from the basal Eagle Ford Group 5a. at USGS Mesozoic locality 14853, 2.5 mi northeast of Al- 1960. Acanthoceras alvaradoense Moreman: Matsumoto, p. 41, text- varado, Johnson County, Texas, is the holotype by mono- fig. 6a-c. 1963. Paracanthoceras amphibolum (Morrow): Haas, p. 18. 1964. typy. Middle Cenomanian Acanthoceras amphibolum Zone. Plesiacanthoceras [amphibolum] (Morrow): Haas, p. 610. Material—A single hypotype, USNM 416062. Description— 1965a. Plesiacanthoceras amphibolum (Morrow): Hattin, pl. 4, figs. J, The specimen is a distorted internal mold K, pl. 5, figs. C-F. just over 60 mm in diameter. Coiling is moderately evolute, 1965b. Plesiacanthoceras amphibolum (Morrow): Hattin, text-fig. 3 with depressed whorls that are trapezoidal in intercostal (8). 1966. Acanthoceras amphibolum Morrow: Matsumoto & section; the costal section is polygonal, with greatest breadth Obata, p. 45, text-figs. 4-6. at the umbilical bullae. Fourteen primary ribs arise at the 1966. Acanthoceras hazzardi Stephenson: Matsumoto & Obata, p. umbilical seam and strengthen into variably developed but 45, text-fig. 7. generally strong umbilical bullae which give rise to coarse, 1968. Plesiacanthoceras [amphibolum Morrow]: Laporte, text-figs. 6- straight, prorsiradiate primary ribs. These bear a strong, 10H. 1968. Acanthoceras amphibolum Morrow: Hattin, p. 1087. conical innermost ventrolateral horn and a low, broad rib 1969. Acanthoceras amphibolum Morrow: Matsumoto, Muramoto & that extends across the venter bearing strong outer ventro- Takahashi, p. 266, pl. 31, fig. 1. lateral and siphonal clavi. One or two short ribs are inter- 1972. Acanthoceras amphibolum Morrow: Cobban & Scott, p. 65, pl. calated between the primaries on the venter and generally 9, pl. 10, figs. 12-16, text-fig. 26. bear clavate outer ventrolateral and siphonal clavi only. As a 1977a. Acanthoceras amphibolum Morrow: Cobban, p. 23, pl. 8, figs. result, there are twice as many outer ventrolateral and 8, 9, pl. 12, figs. 10-12, 15-23, text-fig. 5. siphonal tubercles as inner ventrolateral and umbilical tu- 1977b. Acanthoceras amphibolum Morrow: Cobban, fig. 4n-q. bercles. 1977. Acanthoceras amphibolum Morrow: Hattin, fig. 4 (13). Discussion—This rather poorly preserved specimen, which 1977. Acanthoceras amphibolum Morrow: Kauffman, pl. 15, figs. 1, we compare to C. johnsonianum, is easily distinguished from 2. other acanthoceratids occurring in the present fauna by the 1977a. Acanthoceras alvaradoense Moreman: Cobban, p. 24, pl. 6, figs. 1-7, 11-20, text-fig. 6. ventral ribbing and tuberculation pattern. This matches that of 1977b. Acanthoceras alvaradoense Moreman: Cobban, fig. 3a-i. both the holotype of "Acanthoceras" johnsonianum and other 1978. Acanthoceras amphibolum Morrow: Hattin & Siemers, specimens before us from the same horizon in north-central fig. 5 (14). Texas. Stephenson confused this species with the older Cun- 1978. Acanthoceras amphibolum Morrow: Kauffman, Cobban & ningtoniceras lonsdalei (Adkins, 1928: 244, pl. 26, fig. 5, pl. 27, Eicher, pl. 4, figs. 1, 2. fig. 3) and referred several juveniles of C. johnsonianum to 1979. Acanthoceras amphibolum Morrow: Merewether, Cobban & lonsdalei (Stephenson, 1955, pl. 6, figs. 9-20). The two are Cavanaugh, pl. 1, figs. 1, 2, 8, 9. easily distinguished: lonsdalei has a rounded rather than 1979. Acanthoceras alvaradoense Moreman: Merewether, Cobban & angular/polygonal whorl section and more intercalated ribs Cavanaugh, pl. 1, figs. 3-7. 1985. Acanthoceras amphibolum Morrow: Zaborski, p. 35, figs. 38- whose tubercles are commonly much weaker than those on the 41. primaries. Co-occurring Acanthoceras amphibolum (Morrow, 1985. Plesiacanthoceras amphibolum (Morrow): Atabekian, p. 87. 1935: 470, pl. 49, figs. 1-4, 6, pl. 51, figs. 3, 4, text-fig. 4; see Material—Seven hypotypes, USNM 416063-416066. Di- below) may be superficially similar at small sizes, but at the mensions: diameter of the present specimen, most specimens have USNM D Wb Wh Wb:Wh already developed distant flank ribs and lost the inner 416066 c 73.5(100) 33.2(45.2) 27.7(37.7) ventrolateral and siphonal clavi, leaving a ventrolateral horn and 1.20 24.5(33.3) low siphonal ridge only. 416065 c 63.5(100) 24.8(39.1) 24.5(38.6) Occurrence—Middle Cenomanian Acanthoceras amphi- 1.01 21.2(33.4) bolum Zone of north-central Texas and Cerro de Muleros only. Description—Coiling evolute, with U = 33% approximately; umbilicus shallow, with low, outward-inclined wall. Genus ACANTHOCERAS Neumayr, 1875 Whorl section trapezoidal, with broadly rounded inner flanks, flattened convergent outer flanks, broadly rounded Type species—Ammonites rhotomagensis Brongniart in Cu- ventrolateral shoulder, and flattened venter. Costal section vier & Brongniart, 1822, pl. N, fig. 2a, b; by subsequent polygonal in early growth, thereafter with convex inner designation (de Grossouvre, 1894). flanks, concave outer flanks and concave venter. Our smallest specimens at diameters of approximately 30 mm ACANTHOCERAS AMPHIBOLUM Morrow, 1935 have 17-18 ribs per whorl. Ribs arise at the umbilical seam Figs. 1w-z, cc-ff, 2a, b and strengthen across the wall into long umbilical bullae. 1935. Acanthoceras? amphibolum Morrow, p. 479, pl. 49, figs. 1-4, 6, These give rise to broad, distant, straight prorsiradiate pl. 51, figs. 3, 4, text-fig. 4. primary ribs somewhat weakened on the outer flank. All ribs 1942. Acanthoceras alvaradoense Moreman, p. 205, pl. 32, fig. 6, text- bear strong, clavate, inner ventrolateral tubercles; weaker fig. 2o, t. outer ventrolateral and siphonal clavi are borne on a low, broad, transverse rib. Siphonal clavi are linked by a blunt siphonal ridge with

additional intercalated clavi, while there may also be short Types-Holotype of P. landisi is USNM 166358; paratypes intercalated ventral ribs associated with the additional clavi are USNM 166359-166361 and 166395 from the middle Cen- (Fig. 1cc, dd). These lack inner ventrolateral tubercles. The omanian Acanthoceras amphibolum Zone at USGS Mesozoic intercalated ribs and clavi are rapidly lost, while outer ven- locality D7084, 4.8 km north of Laguna, Valencia County, trolateral clavi decline progressively, first leaving a flat ven- New Mexico. ter and then a progressively more deeply sulcate venter in Material-Five specimens, USNM 416067-416071. Di- costal section (Fig. ly, z), as ventrolateral horns become mensions: progressively larger. Where external shell surface is well USNM D Wb Wh Wb:Wh preserved, a low, blunt siphonal ridge is visible as are del- 416069 c 61.3(100) 24.9(40.6) - icate convex ventral riblets, lirae, and striae, looping between 19.0(31.0) the horns and covering the interspaces between (Figs. lx, y, 416068 c 62.8(100) 29.5(47.0) 24.8(39.5) 2b). USNM 416006 (Fig. 2a, b) has 17 ribs at a diameter of 1.19 19.4(30.9) is 59.1(100) 27.2(47.0) 24.0(40.6) 76.5 mm; USNM 416064 (Fig. ly, z) has 12 or 13 at a 1.13 19.4(32.8) diameter of 107 mm. 416067 c 69.5(100) 29.2(42.0) - Adult body-chamber fragments have intercostal whorl 21.8(31.4) heights of up to 80 mm. The ribs are very distant, with strong bullae that migrate from umbilicolateral to inner lat- Description-Three specimens show the inner whorls to a eral position toward the adult aperture; strong ventrolateral diameter of 70 mm (Fig. 2c, e, h-k). Coiling is involute with horns are linked by weak looped riblets across a venter just over 20% of the previous whorl covered; the umbilicus which is deeply sulcate in costal section. The final rib before is of moderate depth and comprises 31-33% of the diameter the final tubular section of the body chamber is strengthened at this stage. The umbilical wall is flat and sub-vertical, ventrally into a high bar-like flange with the horns with the umbilical shoulder quite narrowly rounded. The disappearing, as mentioned by Stephenson (1955: 62). costal whorl section is depressed trapezoidal, with greatest Suture with broad, moderately incised bifid E/L, narrow L, breadth below mid-flank; the inner flanks are rounded, the mid-outer flanks flattened and covergent, the ventrolateral and broad U2. Discussion-Unpublished work by Cobban has shown shoulders broadly rounded, and the venter somewhat Acanthoceras amphibolum, A. alvaradoense, and A. hazzardi of flattened. The costal whorl section is depressed polygonal, previous authors to be synonyms and strict contemporaries. with the greatest breadth at the umbilical bullae. Twelve to Suggestions that amphibolum sensu stricto and alvaradoense 13 primary ribs arise at the umbilical seam and strengthen were early and late subspecies of amphibolum (Cobban, into prominent bullae that are variable in strength in and 1984a: 77) must be abandoned. Early and late forms certainly between individuals. These bullae give rise to one or rarely exist and differ in that the early whorls of the early form have a pair of broad, blunt, straight, rectiradiate ribs, and single constrictions and nodate ventrolateral and siphonal tubercles, intercalatories arise below mid-flank. All ribs strengthen whereas the early whorls of the later form lack constrictions and are equally developed at the umbilical shoulder where and generally have clavate tubercles (Fig. 1cc, dd); the latter there are estimated 26 ribs per whorl. All ribs bear strong requires a new subspecific name. The present material all conical inner ventrolateral tubercles. A broad transverse rib belongs to the early form of the species, but the synonymy connects these across the broad venter and bears strong encompasses all references to the species. Late forms are davate outer ventrolateral and somewhat weaker siphonal illustrated by Cobban & Scott (1972: 65 [pars], pl. 9, pl. 10, clavi, the latter borne on a feebly developed siphonal ridge. figs. 12-16, text-fig. 26), Cobban (1977a: 23, pl. 8, figs. 8, 9, Beyond a diameter of 75 mm, ornament modifies pl. 12, figs. 10-12, 15-23, text-fig. 5), Kauffman (1977, pl. progressively (Fig. 3), and two large specimens, USNM 15, figs. 1, 2), Kauffman, Cobban & Eicher (1978, pl. 4, figs. 416070 and 416071, reveal a middle growth stage at 150- 1, 2), and Merewether, Cobban & Cavanaugh (1979, pl. 1, 200 mm diameter in which the whorl section is markedly figs. 1, 2, 8, 9). compressed (whorl breadth to height ratio 0.8), with a nar- Occurrence-Middle Cenomanian Acanthoceras amphi- rowly rounded umbilical shoulder, broadly rounded inner bolum Zone, New Mexico, Trans-Pecos and north-central flanks, and flattened, convergent outer flanks with sharp Texas, Kansas, Colorado, Wyoming, South Dakota and ventrolateral shoulders and a shallow concave venter. Montana; Japan; USSR. Zaborski (1985) has recently re- Nearly all tuberculation has disappeared, leaving only corded the species from Nigeria. distant bullae on the umbilical shoulder that give rise to low ribs effaced across the flanks and separated by somewhat Genus PARACOMPSOCERAS Cobban, 1972 deepened and constriction-like interspaces. Suture only imperfectly exposed. Type species-Paracompsoceras landisi Cobban, 1972: 10, Discussion-We initially identified the inner whorls of the pl. 2, figs. 24-26, pls. 6-8, pl. 9, figs. 5-8, text-figs. 9-11; present material as Acanthoceras. Yet they develop outer by original designation. Middle Cenomanian Acanthoceras whorls that are utterly distinct from that genus, matching amphibolum Zone of west-central New Mexico. with the types of P. landisi. The present material differs from Discussion-Paracompsoceras is a heterochronous hom- the holotype and topotypes of the older Acompsoceras bifur- eomorph of Acompsoceras Hyatt, 1903. Whereas the latter is catum Powell (1963: 311, pl. 31, figs. 1, 7, 11, text-fig. 31, r) the probable ancestor of Acanthoceras and typically lower in lacking a lateral tubercle, although it is otherwise very Cenomanian with a wide geographic distribution, the for- similar in early growth stages. It might be argued that this is mer is a middle Cenomanian derivative of Acanthoceras and no more than intraspecific variation, yet it is the relatively is restricted to the Western Interior of the United States. feebly ornamented A. bifurcatum that has this tubercle, The present material is better preserved than the type series coarsely ribbed juvenile P. landisi lacking it. This is the re- and considerably amplifies our knowledge of the early on- verse of the normal pattern of covariance in Acanthocera- togeny of this remarkable genus. tacea, and these two species are maintained separate. Acompsoceras bifurcatum is considered a junior synonym of A. PARACOMPSOCERAS LANDISI Cobban, 1972 inconstans (Schluter, 1871) (Wright & Kennedy, 1987: 143). Figs. 2c, e, h-k, 3 Occurrence-Middle Cenomanian Acanthoceras amphibolum 1972. Paracompsoceras landisi Cobban, p. 10, pl. 2, figs. 24-26, pls. Zone of New Mexico only. 6-8, pl. 9, figs. 5-8, text-figs. 9-11. 1977a. Paracompsoceras landisi Cobban: Cobban, p. 25, pl. 14. Genus TARRANTOCERAS Stephenson, 1955 Type species-Tarrantoceras rotatile Stephenson, 1955 ( = Mantelliceras sellardsi Adkins, 1928), from the middle Cen- omanian Acanthoceras amphibolum Zone of northeastern Texas.

TARRANTOCERAS SELLARDSI (Adkins, 1928) Material—Fourteen fragments. Fig. 2t-w Discussion—Cobban & Scott (1972: 65) pointed out that T. rotatile, T. stantoni, and T. lillianense of Stephenson (1955) 1928. Mantelliceras sellardsi Adkins, p. 239, pl. 25, fig. 1, pl. 26, fig. were no more than variants of a single species, and that 4. view is supported by the present material which varies 1942. Mantelliceras sellardsi Adkins: Moreman, p. 207. 1955. markedly in relative strength of ribbing and degree of dom- Tarrantoceras rotatile Stephenson, p. 59, pl. 5, figs. 1-10. 1955. Tarrantoceras stantoni Stephenson, p. 60, pl. 5, figs. 11-21. 1955. inance of ribs over tubercles. Two large fragments, USNM Tarrantoceras lillianense Stephenson, p. 60, pl. 5, figs. 22-27. 1955. 416073 (Fig. 2v, w) and 416074, 75 and 84 mm in diameter, Tarrantoceras multicostatum Stephenson, p. 61, p1. 6, figs. 21- appear to be incomplete macroconchs; USNM 416072, 57 23. mm in diameter, seems to be a microconch lacking the ter- 1971. Eucalycoceras sellardsi (Adkins): Kennedy, p. 84. minal portion of the body chamber (Fig. 2t, u). 1972. Tarrantoceras rotatile Stephenson: Cobban & Scott, p. 64, pl. 10, Occurrence—Middle Cenomanian Acanthoceras amphibolum figs. 1-11, text-fig. 25. Zone of Texas, New Mexico, southeastern Colorado, and 1977a. Tarrantoceras rotatile Stephenson: Cobban, p. 23, pl. 6, figs. 8- eastern Wyoming. 10, 28-29, p1. 11, figs. 7, 8, 11-16, pl. 12, figs. 13, 14, text- fig. 4. 1977b. Tarrantoceras rotatile Stephenson: Cobban, figs. 3n, o, 4g. 1978. Tarrantoceras rotatile Stephenson: Cooper, p. 92, text-fig. 20. 1978. Suborder ANCYLOCERATINA Wiedmann, 1966 Utaturiceras(?) sellardsi (Adkins): Young & Powell, p. xxv.18. 1984a. Superfamily TURRILITACEAE Gill, 1871 Tarrantoceras sellardsi (Adkins): Cobban, p. 78. Family ANISOCERATIDAE Hyatt, 1900 1986. Tarrantoceras sellardsi (Adkins): Cobban, fig. 3c, d. Types—Holotype TMM 34048, from the lower part of the Genus ANISOCERAS Pictet, 1854 Eagle Ford Group south of Moody, McLennan County, Texas, middle Cenomanian Acanthoceras amphibolum Zone; by Type species—Anisoceras saussureanus Pictet, 1847: 374, pl. 13, monotypy. Hypotypes USNM 416072-416074. figs. 1-4; by original designation. 42

ANISOCERAS cf. PLICATILE (J. Sowerby, 1819) ern and eastern Europe, the USSR, North Africa, Nigeria, Fig. 1aa, bb Angola, Zululand (South Africa), Madagascar, and Moz- Compare: ambique. In the United States there are records from Cal- 1819. Hamites plicatilis J. Sowerby, p. 281, pl. 234, fig. 1. ifornia, Texas, New Mexico, and Colorado; in the Western 1971. Anisoceras plicatile (J. Sowerby): Kennedy, p. 12, pl. 3, figs. Interior the species is particularly widespread in the Acan- 12, 13, pl. 4, figs. 1-3 (with synonymy). thoceras amphibolum Zone, but may range as low as the Con- 1983. Anisoceras plicatile (J. Sowerby): Kennedy & Juignet, p. 25, linoceras tarrantense Zone. figs. 10q—e, 16a—m, p, q, 34e, m. Material—A single fragment, USNM 416075. Class BIVALVIA Linnaeus, 1758 Discussion—The specimen is crushed, with a maximum Subclass PTERIOMORPHIA Beurlen, 1944 apparent whorl height of 18 mm. Large round-based tu- Order PTERIOIDA Newell, 1965 bercles at mid-flank link groups of two or three narrow ribs Suborder OSTREINA Férrusac, 1822 which loop to smaller ?clavate ventrolateral tubercles that Superfamily OSTREACEAE Rafinesque, 1815 are in turn linked over the venter by two or three ribs; there Family OSTREIDAE Rafinesque, 1815 are two, rarely three, nontuberculate ribs that are strong on Subfamily OSTREINAE Rafinesque, 1815 the flanks and venter but somewhat weakened on the dorsum between the tuberculate groups. Rather poor fragments of Genus OSTREA Linnaeus, 1758 Anisoceras are known from the zone of Acanthoceras amphibolum, but these are generally too incomplete to de- Type species—Ostrea edulis Linnaeus, 1758: 696 (ICZN termine whether they are indeed helically coiled as in A. Opinion 94, 1958). plicatile of comparable size or represent some other species. OSTREA BELOITI Logan, 1899 Family TURRILITIDAE Meek, 1876 Fig. 2f, g, m, r Genus TURRILITES Lamarck, 1801 1876. Ostrea elegantula Newberry, p. 33 (nomen oblitum). 1884. Ostrea elongatula Newberry: White, p. 295, pl. 36, figs. 5-7. Subgenus TURRILITES Lamarck, 1801 1899. Ostrea beloiti Logan, p. 214, pl. 25, figs. 7, 8. 1965a. Ostrea beloiti Logan: Hattin, p. 40, pl. 4, figs. A, B, D, G, I. Type species—Turrilites costatus Lamarck, 1801: 102; by 1965b. Ostrea beloiti Logan: Hattin, p. 13, fig. 3.4, 3.9. original designation. 1977a. Ostrea beloiti Logan: Cobban, p. 20, pl. 7, figs. 4-7. 1977b. Ostrea beloiti Logan: Cobban, fig. 4 H. TURRILITES (TURRILITES) ACUTUS Passy, 1832 1977. Ostrea beloiti Logan: Kauffman & Powell, p. 92, pl. 8, figs. 9, Figs. 1h, 2d, 1 10. 1978. Ostrea beloiti Logan: Hattin & Siemers, fig. 5.16, 5.17. 1832. Turrilites acutus Passy, p. 334, pl. 16, figs. 3, 4. 1980. Ostrea beloiti Logan: Cobban & Hook, p. 169, fig. 2A, B. 1977a. Turrilites acutus Passy: Cobban, p. 22, pl. 4, figs. 4, 5. 1984b. Ostrea beloiti Logan: Cobban, p. 13, pl. 5, fig. 11. 1977b. Turrilites acutus Passy: Cobban, figs. 2i, 4k. 1986. Ostrea beloiti Logan: Cobban, fig. 5i. 1983. Turrilites acutus Passy: Kennedy & Juignet, p. 51 (with syn- Types—Lectotype, the original of Logan (1899, pl. 25, figs. onymy). 7, 8). Hypotypes USNM 416079-416082. 1985. Turrilites acutus Passy: Atabekian, p. 77, pl. 28, figs. 5-13, Material—Abundant specimens. pl. 29, figs. 1-10, pl. 30, figs. 1-11 (with synonymy). Types— Lectotype, the original of Passy (1832, pl. 16, fig. 3), from Discussion—Kauffman & Powell (1977: 92, pl. 8, figs. the middle Cenomanian of Rouen, France, designated by 9, 10) described this species in detail, and Cobban & Hook Juignet & Kennedy (1976: 65). Hypotypes USNM 416076- (1980) discussed its stratigraphic and geographic occur- 416078. rences. The present material is very typical. Material—Fourteen fragments. Occurrence—Middle Cenomanian Conlinoceras tarrantense Discussion—Specimens vary from 1.5 to 21 mm in whorl Zone to upper Cenomanian Dunveganoceras pondi Zone. This height. Ribs number 15-16 per whorl in middle growth. oyster is abundant and commonly a rock-former in the middle These ribs arise at the upper whorl suture and are produced Cenomanian Acanthoceras amphibolum Zone ranging from into sharp tubercles at mid-flank. A weakened rib sweeps Manitoba (McNeil & Caldwell, 1974) to west and north- forward to a smaller sharp tubercle located just above the central Texas. lower whorl suture, and a third, much smaller, spirally elongate tubercle lies in notches in the whorl seam. The Suborder PTERIINA Newell, 1965 base of the whorls is smooth. These specimens overlap in Superfamily PTERIACEA Gray, 1847 rib density and ornament with topotypes of Turrilites acutus Family INOCERAMIDAE Giebel, 1852 from Rouen illustrated and described by Juignet & Kennedy (1976: 65, pl. 3, fig. 6, pl. 4, figs. 1-3), and with numerous Genus INOCERAMUS J. Sowerby, 1814 specimens from the middle Cenomanian Acanthoceras rho- Type species—Inoceramus cuvierii J. Sowerby, 1814: 448 tomagense Zone, Turrilites acutus Subzone of Snowdon Hill, (ICZN Opinion 473, 1957). Chard, Somerset (Oxford University Museum collections), which have up to 21 tuberculated ribs per whorl and show a INOCERAMUS ARVANUS Stephenson, 1953 third row of tubercles exposed at the inter-whorl suture. Fig. 2n, q, s These suggest that Turrilites acutus americanus Cobban & Scott (1972: 53, pl. 11, figs. 1-11, text-fig. 21), with 1953. Inoceramus arvanus Stephenson, p. 65, pl. 12, figs. 6-9. estimated 25-26 tuberculated ribs per whorl, may be a 1955. Inoceramus arvanus Stephenson: Stephenson, p. 55, pl. 4, synonym. Certainly the well-preserved Turrilites with only figs. 1-3. 21 ribs from west-central New Mexico (Cobban, 1977a: 22, 1977a. Inoceramus arvanus Stephenson: Cobban, p. 15, pl. 6, fig. 27. 1977b. Inoceramus arvanus Stephenson: Cobban, fig. 3 p. 1977. pl. 4, figs. 4, 5) belongs to acutus sensu stricto, as does the Inoceramus arvanus Stephenson: Kauffman, pl. 4, figs. 6, 7. present material. Types—Holotype USNM 105157, the original of Ste- Occurrence—The species first appears in the middle of phenson (1953: 65, pl. 12, fig. 7); by original designation. the middle Cenomanian, where it is widespread and com- Hypotypes USNM 416083-416085. mon; it ranges to the lower part of the upper Cenomanian, Material—Numerous specimens. where it is generally rare. The species is known from west- Discussion—The present collection includes individuals 43 up to 75 mm in height that show variation in ornament, synonyms and types: Zoological Society of London, Proceedings, outline, and degree to which the shallow posterior fold is 15: 129-219. developed. These specimens overlap with the holotype in Grossouvre, A. de, 1894, Les ammonites de la craie supérieure, morphology. Pt. 2, Paleontologie, of Recherches sur la craie superieure: Carte geologique détaillée de la France, Mémoires, 264 pp. (1893 im- Occurrence-In the Western Interior and Texas, this spe- print) cies is an excellent marker for the Acanthoceras amphibolum Haas, 0., 1963, Paracanthoceras wyomingense (Reagan) from the Zone. Kauffman (1978) recorded the species from the lower Western Interior of the United States and from Alberta (Ammon- and middle Cenomanian of southern England. oidea): American Museum Novitates, no. 2151: 19 pp. Haas, 0., 1964, Plesiacanthoceras, new name for Paracanthoceras Haas, References 1963, non Furon, 1935: Journal of Paleontology, 38 (3): 610. Hattin, D. E., 1965a, Stratigraphy of the Graneros Shale (Upper Adkins, W. S., 1928, Handbook of Texas Cretaceous fossils: Cretaceous) in central Kansas: Kansas Geological Survey, Texas University Bulletin 2838: 385 pp. Bulletin 178: 83 pp. Adkins, W. S. & Lozo, F. E., Jr., 1951, Stratigraphy of the Woodbine Hattin, D. E., 1965b, Upper Cretaceous stratigraphy, paleontology, and Eagle Ford, Waco area, Texas; in Lozo, F. E., Jr. (ed.), The and paleoecology of western Kansas, with a section on Pierre Shale, Woodbine and adjacent strata of the Waco area of central Texas: by W. A. Cobban: Geological Society of America Field Fondren Science Series, no. 4: 101-164. Conference Guidebook, 78th Annual Meetings, 1965, 69 pp. Atabekian, A. A., 1985, Turrilitids of the late Albian and Ceno- Hattin, D. E., 1968, Plesiacanthoceras wyomingense (Reagan) from manian of the southern part of USSR: Academy of Sciences of Graneros Shale and Greenhorn Limestone (Upper Cretaceous) the USSR, Ministry of Geology, Interdepartmental Stratigraphic of central Kansas: Journal of Paleontology, 42 (4): 1084-1090. Committee, Transactions, 14: 112 pp. (in Russian) Hattin, D. E., 1977, Upper Cretaceous stratigraphy, paleontology Beurlen, K., 1944, Beitrage zür Stammesgeschichte der Muschlen: and paleoecology of western Kansas, with a section on Pierre Shale, Sitzungsberichte der Mathematisch-naturwissenschaftlichen by W. A. Cobban: The Mountain Geologist, 14 (3, 4): 175-218. (Abteilung) Klasse der Bayerischen Akademie der Wissenschaf- Hattin, D. E. & Siemers, C. T., 1978, Upper Cretaceous stratigraphy ten zu Munchen, 1944 (1, 2): 133-145. and depositional environments of western Kansas: Kansas Geo- Bose, E., 1910, Monographía geológica y paleontológica del logical Survey, University of Kansas Guidebook Series 3: 102 pp. Cerro de Muleros cerca de ciudad Juarez, Estado de Hyatt, A., 1889, Genesis of the Arietidae: Smithsonian Contribu- Chihuahua, y description de la fauna cretácea de la Encantada, tions to Knowledge, 26 (637): xi + 238 pp.; Harvard Museum placer de Guadalupe, Estado de Chihuahua: Instituto of Comparative Zoology Memoirs, 16 (3): xi + 238 pp. Geologico de Mexico, Boletín 25: 193 pp. Hyatt, A., 1900, Cephlopoda; in Zittel, K. A. von, 1896-1900, Cobban, W. A., 1972, New and little-known ammonites from the Textbook of palaeontology: Macmillan, London, pp. 502-604. Upper Cretaceous (Cenomanian and Turonian) of the western Hyatt, A. (edited by T. W. Stanton), 1903, Pseudoceratites of the interior of the United States: U.S. Geological Survey, Professional Cretaceous: U.S. Geological Survey, Monograph 44: 351 pp. Paper 699: 24 pp. (1971 imprint) Juignet, P. & Kennedy, W. J., 1976, Faunes d'ammonites et bios- Cobban, W. A., 1977a, Characteristic marine molluscan fossils tratigraphie comparée du Cenomanien du nord-ouest de la from the Dakota Sandstone and intertongued Mancos Shale, France (Normandie) et du sud de l'Angleterre: Societe geologique west-central New Mexico: U.S. Geological Survey, Professional de Normandie et Amis du Museum du Havre, 63 (2): 193 pp. Paper 1009: 30 pp. Kauffman, E. G., 1977, Illustrated guide to biostratigraphically Cobban, W. A., 1977b, Fossil mollusks of the Dakota Sandstone important Cretaceous macrofossils, Western Interior basin, and intertongued Mancos Shale of west-central New Mexico; in U.S.A.: The Mountain Geologist, 14 (3, 4): 225-274. San Juan Basin III: New Mexico Geological Society, Kauffman, E. G., 1978, British Middle Cretaceous inoceramid bio- Guidebook 28: 213-220. stratigraphy; in Evénements de la partie moyene du Cretace; Mid- Cobban, W. A., 1984a, Mid-Cretaceous ammonite zones, Western Cretaceous events, Uppsala 1975-Nice 1976: Museum d'Histoire Interior, United States: Geological Society of Denmark, Bulletin, Naturelle de Nice, Annales, 4: iv.1-iv.12. (1976 imprint) 33: 71-89. Kauffman, E. G. & Powell, J. D., 1977, Paleontology; in Cobban, W. A., 1984b, Molluscan record from a mid-Cretaceous Kauffman, E. G., Hattin, D. E. & Powell, J. D., Stratigraphic, borehole in Weston County, Wyoming: U.S. Geological paleontologic, and paleoenvironmental analysis of the Upper Survey, Professional Paper 1271: 24 pp. Cretaceous rocks of Cimarron County, northwestern Oklahoma: Cobban, W. A., 1986, Upper Cretaceous molluscan record from Geological Society of America, Memoir 149: 47-114. Lincoln County, New Mexico: Southwest Section of AAPG, Kauffman, E. G., Cobban, W. A. & Eicher, D. L., 1978, Albian Transactions and Guidebook of 1986 Convention, Ruidoso, through lower Coniacian strata, biostratigraphy and principal New Mexico, pp. 77-89. events, Western Interior United States; in Evénements de la Cobban, W. A. & Hook, S. C., 1980, Occurrence of Ostrea beloiti par-tie moyene du Crétacé; Mid-Cretaceous events, Uppsala Logan in Cenomanian rocks of Trans-Pecos Texas; in New 1975-Nice 1976: Museum d'Histoire Naturelle de Nice, Mexico Geological Society, Guidebook 31: 169-172. Annales, 4: 23.1-23.52. (1976 imprint) Cobban, W. A. & Scott, G. R., 1972, Stratigraphy and ammonite fauna Kennedy, W. J., 1971, Cenomanian ammonites from southern of the Graneros Shale and Greenhorn Limestone near Pueblo, England: Palaeontological Association, Special Papers in Colorado: U.S. Geological Survey, Professional Paper 645: 108 Palaeontology 8: 133 pp.; London. PP. Kennedy, W. J. & Juignet, P., 1983, A revision of the ammonite Collignon, M., 1937, Ammonites cénomaniennes du sud-ouest de faunas of the type Cenomanian. 1, Introduction, Ancyloceratina: Madagascar: Service des Mines (Madagascar), Annales Cretaceous Research, 4: 3-83. géologique, no. 8: 31-69. Kullmann, J. & Wiedmann, J., 1970, Significance of sutures in phy- Cooper, M. R., 1978, Uppermost Cenomanian-basal Turonian logeny of Ammonoidea: University of Kansas Paleontological ammonites from Salinas, Angola: South African Museum, Contributions, Paper 47: 32 pp. Annals, 75 (5): 51-152. Lamarck, J. B. P. A., de, 1801, Système des animaux sans vertèbres: Cuvier, G. & Brongniart, A., 1822, Description geologique des en- J. B. P. A. de Lamarck, Paris, Chez Deterville, 432 pp. virons de Paris: G. Dufor et E. de Ocagne, Paris & Amsterdam, Laporte, L. F., 1968, Ancient environments: Prentice-Hall, 428 pp. Englewood Cliffs, N.J., 116 pp. Férrusac, A. E., de, 1822, Tableaux systematique des animaux Linnaeus, C., 1758, Systema naturae, Editio decima, reformata, v. mollusques: Paris & London, 111 pp. 1: Stockholm, 832 pp. Giebel, C. G., 1852, Deutschlands Petrefacten. Ein systematisches Logan, W. N., 1899, Contributions to the paleontology of the Upper Verzeichniss aller in Deutschland und der angrenzenden Lan- Cretaceous series: Field Columbian Museum, Publication 36, dern vorkommenden Petrefacten nebst Angabe der Synonyme Geological Series, 1 (6): 201-216. und Fundorte: Leipzig, pp. 329-441 (Bivalves). Lovejoy, E. M. P., 1976, Geology of Cerro de Cristo Rey uplift, Gill, T., 1871, Arrangement of the families of mollusks: Chihuahua and New Mexico: New Mexico Bureau of Mines & Smithsonian Miscellaneous Collections, 227: 49 pp. Mineral Resources, Memoir 31: 76 pp. Gray, J. E., 1847, A list of the genera of recent Mollusca, their Matsumoto, T., 1938, Preliminary notes on some of the more im- 44

portant fossils among the Gosyonoura fauna: Geological graph, 68 pp. [1853: 1-26, pls. 1-10; 1854 (1855): 27-36, pls. 11- Society of Japan, 45: 13-24. 16; 1856 (1857): 37-68, pls. 17-27.] Matsumoto, T., 1960, On some type ammonites from the Gulf Sowerby, J., 1812-22, The mineral conchology of Great Britain: B. Coast Cretaceous: Kyushu University, Faculty of Science, Meredith, London, 767 pp., 383 pls. [1812, v. 1: 9-32, pls. 1-9; Science Reports, Geology, 5 (1): 36-49. (in Japanese) 1813, v. 1: 33-96, pls. 10-44; 1814, v. 1: 97-178, pls. 45-78; 1815, Matsumoto, T. & Obata, I., 1966, An acanthoceratid ammonite from v. 1: 179-234, pls. 79-102, and v. 2: 1-28, pls. 103-114; 1816, v. 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